AAI-223 add an endpoint to get registration info based on user's email address

[marius-mather]

Description

AAI-223: there doesn't seem to be a good way to pass the registration info from Auth0 directly to our registration page. Instead, if we want to have app-specific email verification pages (and go directly from them to app login), it looks like we have to:

• Pass the email from Auth0 to the verification page (Auth0 allows this, although it's not well documented)
• Do a lookup from the frontend verification page - call this new API to get the registration source (if it's available)

TODO:

• Document how we pass email from Auth0 to the verification page - requires using the management API to change a setting

Possible issues

• Are there privacy/security concerns around having an endpoint that (theoretically) allows you to check whether a user exists in the system based on email address? Have tried to minimize the amount of info returned, but if the response is anything other than the default of "biocommons", you would know the user is in the system

Changes

• Add /utils/registration_info?user_email=user@example.com endpoint
• Look up user by email in the management API

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have added unit / integration tests that prove my fix is effective or that my feature works
• I have run all tests locally and they pass
• I have updated the documentation (if applicable)

How to Test Manually (if necessary)

Run uv run pytest

[amandazhuyilan]

Looks good - thanks for adding this !