Allow rostering directly from email

[supergi0]

On Team Admin side

• Encode invitation id and a key to a jwt
• Create accept and decline links & corresponding buttons in email template & send email.

On Player side

• Redirect to page, get the token and send call to backend to verify it.
• Get invitation id and follow the same procedure as before.

To test

• Set a EMAIL_SECRET_KEY environment variable.

Email ss

https://imgur.com/a/jj5QcC5

Series invitation error response UI

Series invitation accept UI

Series invitation decline UI

[SibiAkkash]

Hi @supergi0, thanks for your contribution !

[punchagan]

Thanks for taking the time to contribute, @supergi0 ! 🎉

I'd really appreciate if you also put in some more context into the commit messages. The PR description details the changes made, etc., but it would be nice to have the "why" and some more context about the changes in the PR, to make the commits more understandable.

I'll let @SibiAkkash and @Joe2k do the more detailed review, that they already seem to be doing.

Thanks again for the contribution!