Adds DB column for merge request assignee state

This extra column will allow us to support the attention
request feature.
Also added a service to allow for this state column to be updated.

Changelog: added

app/models/concerns/merge_request_reviewer_state.rb

+# frozen_string_literal: true
+
+module MergeRequestReviewerState
+  extend ActiveSupport::Concern
+
+  included do
+    enum state: {
+      unreviewed: 0,
+      reviewed: 1,
+      attention_required: 2
+    }
+
+    validates :state,
+      presence: true,
+      inclusion: { in: self.states.keys }
+  end
+end

app/models/merge_request_assignee.rb

 # frozen_string_literal: true
 
 class MergeRequestAssignee < ApplicationRecord
+  include MergeRequestReviewerState
+
   belongs_to :merge_request, touch: true
   belongs_to :assignee, class_name: "User", foreign_key: :user_id, inverse_of: :merge_request_assignees
 

app/models/merge_request_reviewer.rb

 # frozen_string_literal: true
 
 class MergeRequestReviewer < ApplicationRecord
-  enum state: {
-    unreviewed: 0,
-    reviewed: 1
-  }
-
-  validates :state,
-    presence: true,
-    inclusion: { in: MergeRequestReviewer.states.keys }
+  include MergeRequestReviewerState
 
   belongs_to :merge_request
   belongs_to :reviewer, class_name: 'User', foreign_key: :user_id, inverse_of: :merge_request_reviewers

db/migrate/20211019153615_add_state_to_merge_request_assignees.rb

+# frozen_string_literal: true
+class AddStateToMergeRequestAssignees < Gitlab::Database::Migration[1.0]
+  REVIEW_DEFAULT_STATE = 0
+
+  def change
+    add_column :merge_request_assignees, :state, :smallint, default: REVIEW_DEFAULT_STATE, null: false
+  end
+end

db/schema_migrations/20211019153615

+713efc9673bc6cda8eff4e433c3c85f0cc4b8b8ca7b5cc4308e57a6d0b0040a0
\ No newline at end of file

db/structure.sql

@@ -15699,7 +15699,8 @@ CREATE TABLE merge_request_assignees (
     id bigint NOT NULL,
     user_id integer NOT NULL,
     merge_request_id integer NOT NULL,
-    created_at timestamp with time zone
+    created_at timestamp with time zone,
+    state smallint DEFAULT 0 NOT NULL
 );
 
 CREATE SEQUENCE merge_request_assignees_id_seq

doc/api/graphql/reference/index.md

@@ -16158,6 +16158,7 @@ State of a review of a GitLab merge request.
 
 | Value | Description |
 | ----- | ----------- |
+| <a id="mergerequestreviewstateattention_required"></a>`ATTENTION_REQUIRED` | The merge request is attention_required. |
 | <a id="mergerequestreviewstatereviewed"></a>`REVIEWED` | The merge request is reviewed. |
 | <a id="mergerequestreviewstateunreviewed"></a>`UNREVIEWED` | The merge request is unreviewed. |
 

spec/graphql/types/merge_request_review_state_enum_spec.rb

@@ -12,6 +12,10 @@ RSpec.describe GitlabSchema.types['MergeRequestReviewState'] do
       'UNREVIEWED' => have_attributes(
         description: 'The merge request is unreviewed.',
         value: 'unreviewed'
+      ),
+      'ATTENTION_REQUIRED' => have_attributes(
+        description: 'The merge request is attention_required.',
+        value: 'attention_required'
       )
     )
   end

spec/models/merge_request_assignee_spec.rb

@@ -37,4 +37,6 @@ RSpec.describe MergeRequestAssignee do
       end
     end
   end
+
+  it_behaves_like 'having unique enum values'
 end

spec/models/merge_request_reviewer_spec.rb

@@ -7,6 +7,8 @@ RSpec.describe MergeRequestReviewer do
 
   subject { merge_request.merge_request_reviewers.build(reviewer: create(:user)) }
 
+  it_behaves_like 'having unique enum values'
+
   describe 'associations' do
     it { is_expected.to belong_to(:merge_request).class_name('MergeRequest') }
     it { is_expected.to belong_to(:reviewer).class_name('User').inverse_of(:merge_request_reviewers) }