Allow for GitHub connector to cast user email to lowercase

[thomwatkin]

Preflight Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for an issue that matches the one I want to file, without success.

Problem Description

Follows in the vein of #1725

We have users onboarding that input their emails in lowercase, despite the email being returned from GitHub being CamelCase. Most users assume case-insensitivity in emails, which causes the friction here.

Being able to cast the email to lowercase will allow for a lot less friction in our onboarding processes.

Proposed Solution

I propose to sdd the code that @VF-mbrauer implemented originally in the Microsoft connector to the GitHub connector.

I'd also suggest that the flag be added to the other connectors as well, as I assume that other people might experience similar issues.

Alternatives Considered

No response

Additional Information

No response

[sagikazarmark]

I'd also suggest that the flag be added to the other connectors as well

We are trying to avoid that by introducing a generic layer in #1635

Adding all these flags to every connector introduces a massive maintenance burden and the configuration is already a giant mess.

Reluctantly, but we generally accept these PRs based on demand as an interim solution.

[thomwatkin]

I was actually wondering why so much of it was repeated across the different connectors. Makes a lot of sense!

I can absolutely see the benefit of a generic middleware layer, but it seems like there's been some difficulty in moving it forward in an incremental way without PRs trying to cover every use-case.

In that case I would still appreciate if the flag for just the GitHub connector could be reviewed in the interim.

Additionally, I'll take a stab at adding a Dex Enhacement Proposal for the above issue, as I'd really love to see that moving forward.