add language selection for app provider

changelog/unreleased/enhancement-app-provider-language-selection.md

@@ -0,0 +1,8 @@
+Enhancement: Added language option to the app provider
+
+We've added an language option to the app provider which will in the
+end be passed to the app a user opens so that the web ui is displayed in the users language.
+
+https://github.com/owncloud/ocis/pull/4399
+https://github.com/cs3org/reva/pull/3156
+https://github.com/owncloud/ocis/issues/4367

docs/services/app-registry/apps.md

@@ -245,12 +245,21 @@ See error cases for [Open a file with the app provider](#open-a-file-with-the-ap
     - `write`: user can edit and download in the opening app
     - `read`: user can view and download from the opening app
     - `view`: user can view in the opening app (download is not possible)
+- `lang` (optional)
+  - default (not given): default language of the application (which might maybe use the browser language)
+  - possible value is any ISO 639-1 language code. Examples:
+    - de
+    - en
+    - es
+    - ...
 
 **Request examples**:
 
 ```bash
 curl -X POST 'https://ocis.test/app/open?file_id=ZmlsZTppZAo='
 
+curl -X POST 'https://ocis.test/app/open?file_id=ZmlsZTppZAo=&lang=de'
+
 curl -X POST 'https://ocis.test/app/open?file_id=ZmlsZTppZAo=&app_name=Collabora'
 
 curl -X POST 'https://ocis.test/app/open?file_id=ZmlsZTppZAo=&view_mode=read'
@@ -362,6 +371,17 @@ HTTP status code: 200
   }
   ```
 
+- invalid language code
+
+  HTTP status code: 400
+
+  ```json
+  {
+    "code": "INVALID_PARAMETER",
+    "message": "lang parameter does not contain a valid ISO 639-1 language code"
+  }
+  ```
+
 ### Creating a file with the app provider
 
 **Endpoint**: specified in the capabilities in `new_file_url`, currently `/app/new`