Ensure email comparisons are case-insensitive, emails stored as lowercase

[ikreymer]

• Add a custom EmailStr type which lowercases the full e-mail, not just the domain.
• Ensure EmailStr is used throughout wherever e-mails are used, both for invites and user models
• Tests: update to check for lowercase email responses, e-mails returned from APIs are always lowercase
• Tests: remove tests where '@' was ur-lencoded, should not be possible since POSTing JSON and no url-decoding is done/expected. E-mails should have '@' present.
• Fixes #2083 where invites were rejected due to case differences
• CI: pin pymongo dependency due to latest releases update, update python used for CI
• bump to 1.11.7

[ikreymer]

@tw4l Since we're using EmailStr more strictly now, we can't support url-encoded emails with @ as %40. If we want to support that, should add it to our custom EmailStr to url-decode emails, but I'm not sure if that's needed?

[tw4l]

@tw4l Since we're using EmailStr more strictly now, we can't support url-encoded emails with @ as %40. If we want to support that, should add it to our custom EmailStr to url-decode emails, but I'm not sure if that's needed?

That's fine! Not sure I even meant to encode that part of the email addresses in the tests, that might have been a mistake.