Standardize ACME instruction details

Our Getting Started guides often include instructions for
configuring Let's Encrypt and ACME before starting
Teleport, but not all of these instructions have the same
level of detail, and some are missing some context around
how Teleport uses ACME and why you need to open port 443 on
your Proxy Service host. This change adds an include that
spells out these instructions and invokes the include in the
appropriate guides.

The intention was to include as much relevant information within
the guides themselves to prevent the reader from having to
navigate to other pages.

Closes #6448

docs/pages/application-access/getting-started.mdx

@@ -31,31 +31,17 @@ $ docker run -d -p 3000:3000 grafana/grafana
 ```
 
 ## Step 2/3. Install and configure Teleport
+(!docs/pages/includes/permission-warning.mdx!)
 
 Download the latest version of Teleport for your platform from our
 [downloads page](https://goteleport.com/teleport/download).
 
-Teleport requires a valid TLS certificate to operate and can fetch one automatically
-using Let's Encrypt [ACME](https://letsencrypt.org/how-it-works/) protocol.
-
 We will assume that you have configured DNS records for `teleport.example.com`
 and `*.teleport.example.com` to point to the Teleport node.
 
-(!docs/pages/includes/permission-warning.mdx!)
-
-Let's generate a Teleport config with ACME enabled:
-
-```code
-$ sudo teleport configure --cluster-name=teleport.example.com --acme [email protected] -o file
-```
+Teleport uses TLS to communicate with clients, and can fetch certificates automatically via Let's Encrypt.
 
-<Admonition
-  type="note"
-  title="Web Proxy Port"
->
-  Teleport uses [TLS-ALPN-01](https://letsencrypt.org/docs/challenge-types/#tls-alpn-01)
-  ACME challenge to validate certificate requests which only works on port `443`. Make sure your Teleport proxy is accessible on port `443` when using ACME for certificate management.
-</Admonition>
+(!docs/pages/includes/acme.mdx!)
 
 Now start Teleport and point it to the application endpoint:
 

docs/pages/application-access/guides/connecting-apps.mdx

@@ -59,31 +59,13 @@ In our example:
 - `teleport.example.com` will host the Access Plane.
 - `*.teleport.example.com` will host all of the applications e.g. `grafana.teleport.example.com`.
 
-Teleport can obtain a certificate automatically from Let's Encrypt using
-[ACME](https://letsencrypt.org/how-it-works/) protocol.
-
-Enable ACME in your proxy config:
-
-```yaml
-proxy_service:
-  enabled: "yes"
-  web_listen_addr: "0.0.0.0:443"
-  public_addr: "teleport.example.com:443"
-  acme:
-    enabled: "yes"
-    email: [email protected]
-```
-
-<Admonition
-  type="note"
-  title="Web Proxy Port"
->
-  Teleport uses [TLS-ALPN-01](https://letsencrypt.org/docs/challenge-types/#tls-alpn-01)
-  ACME challenge to validate certificate requests which only works on port `443`.  Make sure your Teleport proxy is accessible on port `443` when using ACME for certificate management.
-</Admonition>
-
-Alternatively, if you have obtained certificate/key pairs for your domain
-(e.g. using [certbot](https://certbot.eff.org/)), they can be provided directly
+You can either configure Teleport to obtain a TLS certificate via Let's Encrypt or use an existing certificate and private key (e.g. using [certbot](https://certbot.eff.org/)).
+<Tabs>
+<TabItem label="Let's Encrypt">
+(!docs/pages/includes/acme.mdx!)
+</TabItem>
+<TabItem label="Existing Credentials">
+If you have obtained certificate/key pairs for your domain they can be provided directly
 to the proxy service:
 
 ```yaml
@@ -97,6 +79,8 @@ proxy_service:
   - key_file: "/etc/letsencrypt/live/*.teleport.example.com/privkey.pem"
     cert_file: "/etc/letsencrypt/live/*.teleport.example.com/fullchain.pem"
 ```
+</TabItem>
+</Tabs>
 
 ### Create a user
 

docs/pages/database-access/getting-started.mdx

@@ -81,25 +81,9 @@ Download the appropriate version of Teleport for your platform from
 our [downloads page](https://goteleport.com/teleport/download).
 
 Teleport requires a valid TLS certificate to operate and can fetch one automatically
-using Let's Encrypt [ACME](https://letsencrypt.org/how-it-works/) protocol.
+using Let's Encrypt.
 
-We will assume that you have configured DNS records for `teleport.example.com` and
-`*.teleport.example.com` to point to the node where you're launching Teleport.
-
-Let's generate a Teleport config with ACME enabled:
-
-```code
-$ teleport configure --cluster-name=teleport.example.com --acme [email protected] > /tmp/teleport.yaml
-```
-
-<Admonition
-  type="warning"
-  title="Web Proxy Port"
->
-  Teleport's ACME protocol integration currently requires web proxy to run on
-  port 443 so open /tmp/teleport.yaml and update `proxy_service.web_listen_addr`
-  and `proxy_service.public_addr` to use port 443 instead of the default 3080.
-</Admonition>
+(!docs/pages/includes/acme.mdx!)
 
 Now start Teleport and point it to your Aurora database instance. Make sure to
 update the database endpoint and region appropriately.

docs/pages/getting-started/linux-server.mdx

@@ -49,18 +49,7 @@ Next, generate a configuration file for Teleport using the `teleport configure`
 
 <Tabs>
   <TabItem label="Public internet deployment with Let's Encrypt">
-  Teleport uses the ACME protocol to request automatic TLS certificates from Let's Encrypt, which accesses an HTTP endpoint on your Teleport host in order to complete authentication challenges.
-
-  Use the following command to configure Teleport:
-
-  ```code
-  $ sudo teleport configure --acme [email protected] --cluster-name=tele.example.com -o file
-  # Wrote config to file "/etc/teleport.yaml". Now you can start the server. Happy Teleporting!
-  ```
-
-  The `--acme-email` flag indicates an email address that Let's Encrypt can use for notifications, and does *not* require the same domain name as your Teleport host. 
-
-  For the `--cluster-name` flag, enter the domain name you used when creating a DNS A record earlier.
+  (!docs/pages/includes/acme.mdx!)
 
   </TabItem>
 

docs/pages/includes/acme.mdx

@@ -0,0 +1,21 @@
+Let's Encrypt verifies that you control the domain name of your Teleport deployment by communicating with the HTTPS server listening on port 443 of your Teleport Proxy Service.
+
+You can configure Teleport to complete the Let's Encrypt verification process—called the ACME protocol—by running the following `teleport configure` command, where `tele.example.com` is the domain name of your Teleport cluster and `[email protected]` is an email address used for notifications (you can use any domain):
+
+```code
+teleport configure --acme [email protected] --cluster-name=tele.example.com
+```
+
+The `--acme`, `--acme-email`, and `--cluster-name` flags will add the following settings to your Teleport configuration file:
+
+```yaml
+proxy_service:
+  enabled: "yes"
+  web_listen_addr: :443
+  public_addr: tele.example.com:443
+  acme:
+    enabled: "yes"
+    email: [email protected]
+```
+
+Port 443 on your Teleport Proxy Service host must allow traffic from all sources.

docs/pages/includes/database-access/start-auth-proxy.mdx

@@ -3,24 +3,13 @@ Download the latest version of Teleport for your platform from our
 installation [instructions](../../installation.mdx).
 
 Teleport requires a valid TLS certificate to operate and can fetch one automatically
-using Let's Encrypt [ACME](https://letsencrypt.org/how-it-works/) protocol. We
+using Let's Encrypt. We
 will assume that you have configured DNS records for `teleport.example.com` and
 `*.teleport.example.com` to point to the Teleport node.
 
-Generate Teleport config with ACME enabled:
+(!docs/pages/includes/acme.mdx!)
 
-```code
-$ teleport configure --cluster-name=teleport.example.com --acme [email protected] -o file
-```
-
-<Admonition type="note" title="Web Proxy Port">
-  Teleport uses [TLS-ALPN-01](https://letsencrypt.org/docs/challenge-types/#tls-alpn-01)
-  ACME challenge to validate certificate requests which only works on port `443`.
-  As such, in order to use ACME for certificate management, web proxy needs to
-  be accessible on port `443`.
-</Admonition>
-
-Start Teleport Auth and Proxy services:
+Next, start the Teleport Auth and Proxy services:
 
 ```code
 $ sudo teleport start

docs/pages/server-access/getting-started.mdx

@@ -70,15 +70,9 @@ This guide introduces some of these common scenarios and how to interact with Te
 
 3. Configure Teleport on the *Bastion Host*.
 
-   Teleport will now automatically acquire an X.509 certificate using the ACME protocol.
+   Teleport uses TLS to communicate with clients, and can fetch certificates automatically via Let's Encrypt.
 
-   ```code
-   # Configure Teleport with TLS certs
-   $ sudo teleport configure \
-     --acme [email protected] \
-     --cluster-name=tele.example.com \
-     -o file
-   ```
+   (!docs/pages/includes/acme.mdx!)
 
    Run the command above on `tele.example.com`.