BugFix when ID is a UUID

[rhenter]

I had a JSON Encode Serialize error when I use a Model with ID as UUID.

    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type UUID is not JSON serializable

[rhenter]

I'll create a test to don't decrease the coverage

[manelclos]

Hi @rhenter, this LGTM, can you please add an example to the test_app using the UUID, it would help a lot to test your changes.