Replace owner check with team owner method check

Add tests

app/models/issue.rb

@@ -584,7 +584,7 @@ class Issue < ApplicationRecord
   def readable_by?(user)
     if user.can_read_all_resources?
       true
-    elsif project.owner == user
+    elsif project.personal? && project.team.owner?(user)
       true
     elsif confidential? && !assignee_or_author?(user)
       project.team.member?(user, Gitlab::Access::REPORTER)

app/models/project_team.rb

@@ -107,6 +107,10 @@ class ProjectTeam
       end
   end
 
+  def owner?(user)
+    owners.include?(user)
+  end
+
   def import(source_project, current_user = nil)
     target_project = project
 

spec/models/project_team_spec.rb

@@ -77,6 +77,32 @@ RSpec.describe ProjectTeam do
     end
   end
 
+  describe 'owner methods' do
+    context 'personal project' do
+      let(:project) { create(:project) }
+      let(:owner) { project.owner }
+
+      specify { expect(project.team.owners).to contain_exactly(owner) }
+      specify { expect(project.team.owner?(owner)).to be_truthy }
+    end
+
+    context 'group project' do
+      let(:group) { create(:group) }
+      let(:project) { create(:project, group: group) }
+      let(:user1) { create(:user) }
+      let(:user2) { create(:user) }
+
+      before do
+        group.add_owner(user1)
+        group.add_owner(user2)
+      end
+
+      specify { expect(project.team.owners).to contain_exactly(user1, user2) }
+      specify { expect(project.team.owner?(user1)).to be_truthy }
+      specify { expect(project.team.owner?(user2)).to be_truthy }
+    end
+  end
+
   describe '#fetch_members' do
     context 'personal project' do
       let(:project) { create(:project) }