Override the 'sub' parameter in the user data tokens

Adding the optional subject key configuration in the form.

This allows the admin to choose which immutable token parameter to use as the mapping between Azure AD accounts and Drupal users.

• "sub" is unique per user, but varies across AD application registrations.
• "oid" is unique per user and common accross all applications in the same tenant.
• See https://docs.microsoft.com/en-us/azure/active-directory/develop/active-d... for further details.

The default "sub" is sufficient in most cases. However "oid" is useful if you want to use AD auth tokens to request access to other services and verify the user id. For example the windows graph API does not return the sub, but will return the oid in its "id" parameter. Also to sync databases between environments that use different app registrations, users will not map properly if "sub" is used.