In commit fc58c35c0, we added a check in various emails for the
settings.CORPORATE_ENABLED value, but that context is only always
included for views/templates with a request.
Here we add that to common_context, which is often used when there
is not a request (like with emails). And we manually add it to the
email context in various cases when there is not a user account to
call with common_context: new user invitations, registration emails,
and realm reactivation emails.
06dd7a3a68