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/models/user.rb

@@ -46,6 +46,8 @@ class User < ApplicationRecord
   belongs_to :account, inverse_of: :user, required: true
   accepts_nested_attributes_for :account
 
+  has_many :applications, class_name: 'Doorkeeper::Application', as: :owner
+
   validates :locale, inclusion: I18n.available_locales.map(&:to_s), if: :locale?
   validates_with BlacklistedEmailValidator, if: :email_changed?
 
@@ -108,6 +110,17 @@ class User < ApplicationRecord
     settings.noindex
   end
 
+  def token_for_app(a)
+    return nil if a.nil? || a.owner != self
+    Doorkeeper::AccessToken
+      .find_or_create_by(application_id: a.id, resource_owner_id: id) do |t|
+
+      t.scopes = a.scopes
+      t.expires_in = Doorkeeper.configuration.access_token_expires_in
+      t.use_refresh_token = Doorkeeper.configuration.refresh_token_enabled?
+    end
+  end
+
   def activate_session(request)
     session_activations.activate(session_id: SecureRandom.hex,
                                  user_agent: request.user_agent,