Some fixes for Apple backend:

[maiiku]

Proposed changes

• add ability for users to supply aud for JWT as a list. This enables apple backednd to be used by both iOS login and web from / other sources login, because iOS provides bundle id as client and web from login requires service id to be supplied (to match against defined return urls and allowed domains)
• if there's no first/last name in the response return None so that the User model is not updated to empty strings if user_details is used in the pipeline

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solves #464

[omab]

Thanks!