Add a md file for Environment (Angular)

docs/en/UI/Angular/Environment.md

@@ -0,0 +1,109 @@
+# Environment
+
+Every application needs some ** environment ** variables. In Angular world, this is usually managed by `environment.ts`, `environment.prod.ts` and so on. It is the same for ABP as well. 
+
+Current `Environment` configuration holds sub config classes as follows:
+
+```typescript
+export interface Environment {
+  apis: Apis;
+  application: Application;
+  oAuthConfig: AuthConfig;
+  production: boolean;
+  remoteEnv?: RemoteEnv;
+}
+```
+
+## Apis
+
+```typescript
+export interface Apis {
+  [key: string]: ApiConfig;
+  default: ApiConfig;
+}
+
+export interface ApiConfig {
+  [key: string]: string;
+  rootNamespace?: string;
+  url: string;
+}
+```
+
+Api config has to have a default config and it may have some additional ones for different modules.
+I.e. you may want to connect to different Apis for different modules. 
+
+Take a look at following example
+
+```json
+{
+  // ...
+  "apis": {
+    "default": {
+      "url": "https://localhost:8080",
+    },
+    "AbpIdentity": {
+      "url": "https://localhost:9090",
+    }
+  },
+  // ...
+}
+```
+
+When an api from `AbpIdentity` is called, the request will be sent to `"https://localhost:9090"`. 
+Everything else will be sent to `"https://localhost:8080"`
+
+* `rootNamespace` **(new)** : Root namespace of the related API. e.g. Acme.BookStore
+
+## Application
+
+```typescript
+ export interface Application {
+  name: string;
+  baseUrl?: string;
+  logoUrl?: string;
+}
+```
+
+* `name`: Name of the backend Application. It is also used by `logo.component` if `logoUrl` is not provided.
+* `logoUrl`: Url of the application logo. It is used by `logo.component`
+* `baseUrl`: [For detailed information](./Multi-Tenancy.md#domain-tenant-resolver)
+
+
+## AuthConfig
+
+For authentication, we use angular-oauth2-oidc. Please check their [docs](https://github.com/manfredsteyer/angular-oauth2-oidc) out
+
+## RemoteEnvironment
+
+Some applications need to integrate an existing config into the `environment` used throughout the application. 
+Abp Framework supports this out of box.
+
+To integrate an existing config json into the `environment`, you need to set `remoteEnv`
+
+```typescript
+export type customMergeFn = (
+  localEnv: Partial<Config.Environment>,
+  remoteEnv: any,
+) => Config.Environment;
+
+export interface RemoteEnv {
+  url: string;
+  mergeStrategy: 'deepmerge' | 'overwrite' | customMergeFn;
+  method?: string;
+  headers?: ABP.Dictionary<string>;
+}
+```
+
+* `url` *: Required. The url to be used to retrieve environment config
+* `mergeStrategy` *: Required. Defines how the local and the remote `environment` json will be merged
+  * `deepmerge`: Both local and remote `environment` json will be merged recursively. If both configs have same nested path, the remote `environment` will be prioritized. 
+  * `overwrite`: Remote `environment` will be used and local environment will be ignored.
+  * `customMergeFn`: You can also provide your own merge function as shown in the example. It will take two parameters, `localEnv: Partial<Config.Environment>` and `remoteEnv` and it needs to return a `Config.Environment` object.
+* `method`: HTTP method to be used when retrieving environment config. Default: `GET`
+* `headers`: If extra headers are needed for the request, it can be set through this field.
+
+
+## What's Next?
+
+* [Service Proxies](./Service-Proxies.md)
+

docs/en/UI/Angular/Migration-Guide-v3.md

@@ -473,5 +473,5 @@ Some interfaces have long been marked as deprecated and now they are removed.
 
 ## What's Next?
 
-* [Service Proxies](./Service-Proxies.md)
+* [Environment](./Environment.md)
 

docs/en/docs-nav.json

@@ -219,11 +219,11 @@
           "items": [
             {
               "text": "Email Sending System",
-              "path": "Emailing.md",
+              "path": "Emailing.md"
             },
             {
               "text": "MailKit Integration",
-              "path": "MailKit.md",
+              "path": "MailKit.md"
             }
           ]
         },
@@ -423,6 +423,10 @@
               "text": "Migration Guide v2.x to v3",
               "path": "UI/Angular/Migration-Guide-v3.md"
             },
+            {
+              "text": "Environment",
+              "path": "UI/Angular/Environment.md"
+            },
             {
               "text": "Service Proxies",
               "path": "UI/Angular/Service-Proxies.md"