[SaaS, Introductory email] - send email 1 day after renewal

Description

As part of &7229 (closed), we will be sending few mails 1 day after a subscription has been purchased or renewed.

Using the mailer introduced in #3999 (closed) and the selector introduced in #4000 (closed) to send an email 1 day after a subscription has been renewed to make them aware of how users are counted and how overages are handled.

Implementation plan

create mailers	#3999 (closed)
MVC identify CustomersDot emails to send to	#4000 (closed)
send introductory email 1 day after purchase	#4007 (closed)
send introductory email 1 day after renewal	👈 you are here
query GitLab.com for group owners emails and send	#4009 (closed)

Tasks

Queue email to send 1 day after renewal