Add user notes on accounts (#14148)

* Add UserNote model

* Add UI for user notes

* Put comment in relationships entity

* Add API to create user notes

* Copy user notes to new account when receiving a Move activity

* Address some of the review remarks

* Replace modal by inline edition

* Please CodeClimate

* Button design changes

* Change design again

* Cancel note edition when pressing Escape

* Fixes

* Tweak design again

* Move “Add note” item, and allow users to add notes to themselves

* Rename UserNote into AccountNote, rename “comment” Relationship attribute to “note”

app/controllers/api/v1/accounts/notes_controller.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+class Api::V1::Accounts::NotesController < Api::BaseController
+  include Authorization
+
+  before_action -> { doorkeeper_authorize! :write, :'write:accounts' }
+  before_action :require_user!
+  before_action :set_account
+
+  def create
+    if params[:comment].blank?
+      AccountNote.find_by(account: current_account, target_account: @account)&.destroy
+    else
+      @note = AccountNote.find_or_initialize_by(account: current_account, target_account: @account)
+      @note.comment = params[:comment]
+      @note.save! if @note.changed?
+    end
+    render json: @account, serializer: REST::RelationshipSerializer, relationships: relationships_presenter
+  end
+
+  private
+
+  def set_account
+    @account = Account.find(params[:account_id])
+  end
+
+  def relationships_presenter
+    AccountRelationshipsPresenter.new([@account.id], current_user.account_id)
+  end
+end