feat: allow connecting social logins to existing users even if emails don't match

When calling /oauth/:provider adds a new query arg connect which needs to contain a valid JWT. If the social login doesn't already exist, sign-ins successfully and the JWT belongs to a valid user, the social login is connected to the user even if the email addresses don't match.

Before submitting this PR:

Checklist

[x] No breaking changes
[x] Tests pass
[ ] New features have new tests
[ ] Documentation is updated

Breaking changes

Avoid breaking changes and regressions. If you feel it is unavoidable, make it explicit in your PR comment so we can review it and see how to handle it.

Tests

please make sure your changes pass the current tests (Use the make test or the make watch command).
if you are introducing a new feature, please write as much tests as possible.

Documentation

Please make sure the documentation is updated accordingly, in particular:

Workflows. Workflows are Mermaid sequence diagrams
Schema. The schema in a Mermaid ER diagram
Environment variables. Please adjust the .env.example file accordingly
OpenApi specifications. We are using inline JSDoc annotations

nhost / hasura-auth