Fix #5104 - GET /api/v1/apps/verify_credentials to confirm app works (#5112)

app/controllers/api/v1/apps/credentials_controller.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class Api::V1::Apps::CredentialsController < Api::BaseController
+  before_action -> { doorkeeper_authorize! :read }
+
+  respond_to :json
+
+  def show
+    render json: doorkeeper_token.application, serializer: REST::StatusSerializer::ApplicationSerializer
+  end
+end

app/controllers/api/v1/apps_controller.rb

@@ -1,8 +1,6 @@
 # frozen_string_literal: true
 
 class Api::V1::AppsController < Api::BaseController
-  respond_to :json
-
   def create
     @app = Doorkeeper::Application.create!(application_options)
     render json: @app, serializer: REST::ApplicationSerializer