Swappable user model

[jayvdb]

Many models fail if the project has swapped in a new user model

timepiece.UserProfile.user: (fields.E301) Field defines a relation with the model 'auth.User', which has been swapped out.
        HINT: Update the relation to point at 'settings.AUTH_USER_MODEL'

[panatale1]

@jayvdb Thanks so much! I'll make sure this is updated when I release the new version for Python 3.8+ and Django 4.2+ in a couple weeks

[panatale1]

Support for custom user models has been added in branch version-upgrade. I will close this issue when the branch is merged and packaged