Add relation for CustomEmoji to creator

Custom Emoji belongs to a creator, which is a User. And a User has many
created Custom Emoji.

app/models/custom_emoji.rb

@@ -6,6 +6,7 @@ class CustomEmoji < ApplicationRecord
   belongs_to :namespace, inverse_of: :custom_emoji
 
   belongs_to :group, -> { where(type: 'Group') }, foreign_key: 'namespace_id'
+  belongs_to :creator, class_name: "User", inverse_of: :created_custom_emoji
 
   # For now only external emoji are supported. See https://gitlab.com/gitlab-org/gitlab/-/issues/230467
   validates :external, inclusion: { in: [true] }
@@ -15,6 +16,7 @@ class CustomEmoji < ApplicationRecord
   validate :valid_emoji_name
 
   validates :group, presence: true
+  validates :creator, presence: true
   validates :name,
     uniqueness: { scope: [:namespace_id, :name] },
     presence: true,

app/models/user.rb

@@ -179,6 +179,7 @@ class User < ApplicationRecord
   has_many :merge_request_reviewers, inverse_of: :reviewer
   has_many :assigned_issues, class_name: "Issue", through: :issue_assignees, source: :issue
   has_many :assigned_merge_requests, class_name: "MergeRequest", through: :merge_request_assignees, source: :merge_request
+  has_many :created_custom_emoji, class_name: 'CustomEmoji', inverse_of: :creator
 
   has_many :bulk_imports
 

spec/factories/custom_emoji.rb

@@ -6,5 +6,6 @@ FactoryBot.define do
     namespace
     group
     file { 'https://gitlab.com/images/partyparrot.png' }
+    creator { namespace.owner }
   end
 end

spec/models/custom_emoji_spec.rb

@@ -4,8 +4,10 @@ require 'spec_helper'
 
 RSpec.describe CustomEmoji do
   describe 'Associations' do
-    it { is_expected.to belong_to(:namespace) }
+    it { is_expected.to belong_to(:namespace).inverse_of(:custom_emoji) }
+    it { is_expected.to belong_to(:creator).inverse_of(:created_custom_emoji) }
     it { is_expected.to have_db_column(:file) }
+    it { is_expected.to validate_presence_of(:creator) }
     it { is_expected.to validate_length_of(:name).is_at_most(36) }
     it { is_expected.to validate_presence_of(:name) }
     it { is_expected.to have_db_column(:external) }
@@ -36,7 +38,7 @@ RSpec.describe CustomEmoji do
       new_emoji = build(:custom_emoji, name: old_emoji.name, namespace: old_emoji.namespace, group: group)
 
       expect(new_emoji).not_to be_valid
-      expect(new_emoji.errors.messages).to eq(name: ["has already been taken"])
+      expect(new_emoji.errors.messages).to include(name: ["has already been taken"])
     end
 
     it 'disallows non http and https file value' do

spec/models/user_spec.rb

@@ -101,6 +101,7 @@ RSpec.describe User do
     it { is_expected.to have_many(:reviews).inverse_of(:author) }
     it { is_expected.to have_many(:merge_request_assignees).inverse_of(:assignee) }
     it { is_expected.to have_many(:merge_request_reviewers).inverse_of(:reviewer) }
+    it { is_expected.to have_many(:created_custom_emoji).inverse_of(:creator) }
 
     describe "#user_detail" do
       it 'does not persist `user_detail` by default' do