Added generic connector for Twitter API

examples/generic_connector_configs/README.md

@@ -7,6 +7,7 @@
   * [OAuth 2.0 API](#oauth-20-api)
   * [Slack Web API](#slack-web-api)
   * [Splunk API](#splunk-api)
+  * [Twitter API](#twitter-api)
 * [Contributing](#contributing)
 
 ## Introduction
@@ -217,6 +218,62 @@ to the backend server uses SSL.
 
 ___
 
+### Twitter API
+This example can be used to interact with [Twitter's API](https://api.slack.com/apis).
+
+The configuration file for the Splunk Web API can be found at [twitter_secretless.yml](./twitter_secretless.yml).
+
+**Note:** This configuration currently only supports connecting to the Twitter API via OAuth2. An issue can be found here for adding an OAuth1 Connector for
+Twitter.
+
+#### How to use this connector
+* Edit the supplied service configuration to get your
+[OAuth token](https://developer.twitter.com/en/docs/basics/authentication/oauth-2-0/bearer-tokens)
+* Run secretless with the supplied configuration(s)
+* Query the API using `http_proxy=localhost:8051 curl api.twitter.com/{Request}`
+
+#### Example Usage
+<details>
+  <summary><b>How to use this connector locally</b></summary>
+  <ol>
+    <li>
+      Get your
+      <a href="https://developer.twitter.com/en/apps">
+        Twitter API key and Secret Key
+      </a>
+    </li>
+    <li>
+      Get an
+      <a href="https://developer.twitter.com/en/docs/basics/authentication/oauth-2-0/bearer-tokens">
+        OAuth token
+      </a>
+      from Twitter through CURL
+    </li>
+    <code>
+      curl -u 'API key:API secret key' \
+      <br />
+      --data 'grant_type=client_credentials' \
+      <br />
+      'https://api.twitter.com/oauth2/token'
+    </code>
+    <li>Save the local token from the request into the OSX keychain</li>
+    <li>Run Secretless locally</li>
+    <code>
+      ./dist/darwin/amd64/secretless-broker \
+      <br />
+      -f examples/generic_connector_configs/twitter_secretless.yml
+    </code>
+    <li>
+      On another terminal window, make a request to Twitter using Secretless
+    <li>
+    <code>
+      http_proxy=localhost:8051 curl "api.twitter.com/1.1/followers/ids.json?screen_name=twitterdev"
+    </code>
+  </ol>
+</details>
+
+___
+
 ## Contributing
 
 Do you have an HTTP service that you use? Can you write a Secretless generic

examples/generic_connector_configs/twitter_secretless.yml

@@ -0,0 +1,16 @@
+version: 2
+services:
+  twitter-oauth2:
+    connector: generic_http
+    listenOn: tcp://0.0.0.0:8051
+    credentials:
+      token:
+        from: keychain
+        get: summon#twitter/bearer-token
+    config:
+      headers:
+        authorization: Bearer {{ .token }}
+        content-type: application/json
+      forceSSL: true
+      authenticateURLsMatching:
+        - ^http[s]*\:\/\/api\.twitter\.com*