What kind of change does this PR introduce?

Add a client parameter to get_jwt_config so people can use client.id_token_signed_response_alg in get_jwt_config.

Supersedes #843
Related to #806. It does not fix it because client.id_token_signed_response_alg should be the default, but at least it allows for a smooth transition.

Checklist

• The commits follow the conventional commits specification.
• You ran the linters with prek.
• You wrote unit test to demonstrate the bug you are fixing, or to stress the feature you are bringing.
• You reached 100% of code coverage on the code you edited, without abusive use of pragma: no cover
• If this PR is about a new feature, or a behavior change, you have updated the documentation accordingly.

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