FEATURE: send max 200 emails every minute for bulk invites (#7875)

DEV: deprecate `invite.via_email` in favor of `invite.emailed_status`

This commit adds a new column `emailed_status` in `invites` table for
 tracking email sending status.
 0 - not required
 1 - pending
 2 - bulk pending
 3 - sending
 4 - sent

For normal email invites, invite record is created with emailed_status
 set to 'pending'.

When bulk invites are sent invite record is created with emailed_status
 set to 'bulk pending'.

For invites that generates link, invite record is created with
 emailed_status set to 'not required'.

When invite email is in queue emailed_status is updated to 'sending'

Once the email is sent via `InviteEmail` job the invite emailed_status
 is updated to 'sent'.

spec/jobs/process_bulk_invite_emails_spec.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Jobs::ProcessBulkInviteEmails do
+  describe '#execute' do
+    it 'processes pending invites' do
+      invite = Fabricate(:invite, emailed_status: Invite.emailed_status_types[:bulk_pending])
+
+      described_class.new.execute({})
+
+      invite.reload
+      expect(invite.emailed_status).to eq(Invite.emailed_status_types[:sending])
+      expect(Jobs::InviteEmail.jobs.size).to eq(1)
+      expect(Jobs::ProcessBulkInviteEmails.jobs.size).to eq(1)
+    end
+  end
+end