Add invitation reminder emails worker implementation

app/workers/member_invitation_reminder_emails_worker.rb

@@ -10,6 +10,10 @@ class MemberInvitationReminderEmailsWorker # rubocop:disable Scalability/Idempot
   def perform
     return unless Gitlab::Experimentation.enabled?(:invitation_reminders)
 
-    # To keep this MR small, implementation will be done in another MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/42981/diffs?commit_id=8063606e0f83957b2dd38d660ee986f24dee6138
+    Member.not_accepted_invitations.not_expired.last_ten_days_excluding_today.find_in_batches do |invitations|
+      invitations.each do |invitation|
+        Members::InvitationReminderEmailService.new(invitation).execute
+      end
+    end
   end
 end

spec/workers/member_invitation_reminder_emails_worker_spec.rb

@@ -6,13 +6,19 @@ RSpec.describe MemberInvitationReminderEmailsWorker do
   describe '#perform' do
     subject { described_class.new.perform }
 
+    before do
+      create(:group_member, :invited, created_at: 2.days.ago)
+    end
+
     context 'feature flag disabled' do
       before do
         stub_experiment(invitation_reminders: false)
       end
 
-      it 'does not raise an error' do
-        expect { subject }.not_to raise_error
+      it 'does not attempt to execute the invitation reminder service' do
+        expect(Members::InvitationReminderEmailService).not_to receive(:new)
+
+        subject
       end
     end
 
@@ -21,8 +27,12 @@ RSpec.describe MemberInvitationReminderEmailsWorker do
         stub_experiment(invitation_reminders: true)
       end
 
-      it 'does not raise an error' do
-        expect { subject }.not_to raise_error
+      it 'executes the invitation reminder email service' do
+        expect_next_instance_of(Members::InvitationReminderEmailService) do |service|
+          expect(service).to receive(:execute)
+        end
+
+        subject
       end
     end
   end