User creation fails when email longer than 50 characters

[djuber]

Describe the bug

We validate user's email addresses to be at most 50 characters, and in some cases reject user creation when that limit is exceeded.

However, local parts of email addresses can by quite long, and domain name components can be up to 63 characters.

While this impacts user's trying to set their own email address, and some signups, and in those cases the error message is actionable, invited users don't have an option to set an alternate email address when their password is saved, and oauth users see a login failure without with an explanation.

To Reproduce

As an example experiment, I tried to invite my hypothetical local pizza parlor owner Frank to my Forem, his email is frank.giuseppe@frankgiuseppesoriginalneapolitan.pizza (okay, totally contrived example of a valid but long-ish email, this is 53 characters long).

I'm able to invite him (via http://localhost:3000/admin/invitations), since validations are skipped when creating the stub user, but he's unable to set his password (since his user can't be saved in this state).

As a second experiment, add a long enough email alias (maybe "your.name+areallylongignoredbygooglesmailserverspart@gmail.com"?) and add this to an available oauth provider's account (twitter, for example), then attempt to sign up.

Expected behavior

We probably need to relax this email width requirement, or remove email addresses that fail validation.

If this validation and length limit are preserved, it should be checked before sending invites for user's that would not be able to sign in afterward.

Screenshots
User invited

But can't set a password after accepting the invite

Sign in from twitter with long email example

Additional context

https://app.honeybadger.io/projects/66984/faults/82641164 this happens to twitter users sometimes, error is
ActiveRecord::RecordInvalid: Validation failed: Email is too long (maximum is 50 characters) when calling Authentication::Authenticator#find_or_create_user! and attempting to save the (invalid) user record.

[github-actions]

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