Implement v4 endpoints for OAuth (#6040)

* Implement POST /oauth/apps endpoint for APIv4

* Implement GET /oauth/apps endpoint for APIv4

* Implement GET /oauth/apps/{app_id} and /oauth/apps/{app_id}/info endpoints for APIv4

* Refactor API version independent oauth endpoints

* Implement DELETE /oauth/apps/{app_id} endpoint for APIv4

* Implement /oauth/apps/{app_id}/regen_secret endpoint for APIv4

* Implement GET /user/{user_id}/oauth/apps/authorized endpoint for APIv4

* Implement POST /oauth/deauthorize endpoint

i18n/en.json

@@ -3611,6 +3611,10 @@
     "id": "model.authorize.is_valid.expires.app_error",
     "translation": "Expires in must be set"
   },
+  {
+    "id": "model.authorize.is_valid.response_type.app_error",
+    "translation": "Invalid response type"
+  },
   {
     "id": "model.authorize.is_valid.redirect_uri.app_error",
     "translation": "Invalid redirect uri"