Application prefs section (#2758)

* Add code for creating/managing apps to settings section

* Add specs for app changes

* Fix controller spec

* Fix view file I pasted over by mistake

* Add locale strings. Add 'my apps' to nav

* Add Client ID/Secret to App page. Add some visual separation

* Fix rubocop warnings

* Fix embarrassing typo

I lost an `end` statement while fixing a merge conflict.

* Add code for creating/managing apps to settings section

- Add specs for app changes
- Add locale strings. Add 'my apps' to nav
- Add Client ID/Secret to App page. Add some visual separation
- Fix some bugs/warnings

* Update to match code standards

* Trigger notification

* Add warning about not sharing API secrets

* Tweak spec a bit

* Cleanup fixture creation by using let!

* Remove unused key

* Add foreign key for application<->user

app/controllers/settings/applications_controller.rb

@@ -0,0 +1,65 @@
+# frozen_string_literal: true
+
+class Settings::ApplicationsController < ApplicationController
+  layout 'admin'
+
+  before_action :authenticate_user!
+
+  def index
+    @applications = current_user.applications.page(params[:page])
+  end
+
+  def new
+    @application = Doorkeeper::Application.new(
+      redirect_uri: Doorkeeper.configuration.native_redirect_uri,
+      scopes: 'read write follow'
+    )
+  end
+
+  def show
+    @application = current_user.applications.find(params[:id])
+  end
+
+  def create
+    @application = current_user.applications.build(application_params)
+    if @application.save
+      redirect_to settings_applications_path, notice: I18n.t('application.created')
+    else
+      render :new
+    end
+  end
+
+  def update
+    @application = current_user.applications.find(params[:id])
+    if @application.update_attributes(application_params)
+      redirect_to settings_applications_path, notice: I18n.t('generic.changes_saved_msg')
+    else
+      render :show
+    end
+  end
+
+  def destroy
+    @application = current_user.applications.find(params[:id])
+    @application.destroy
+    redirect_to settings_applications_path, notice: t('application.destroyed')
+  end
+
+  def regenerate
+    @application = current_user.applications.find(params[:application_id])
+    @access_token = current_user.token_for_app(@application)
+    @access_token.destroy
+
+    redirect_to settings_application_path(@application), notice: t('access_token.regenerated')
+  end
+
+  private
+
+  def application_params
+    params.require(:doorkeeper_application).permit(
+      :name,
+      :redirect_uri,
+      :scopes,
+      :website
+    )
+  end
+end