Invitation creation should send an email

[zaratan]

Why ?

Because it's not obvious that you have been invited until you get a notification. Sending an email is a good way to do it.

Must Have

• [ ] After an invite creation an email should be sent
• [ ] The email should contain a token of sort (hint uuid works here) to be able to identify a returning user.

Reading list

• https://guides.rubyonrails.org/action_mailer_basics.html