Using AnonymousCredentials instead of Mock

[ramuta]

Try using AnonymousCredentials instead of the Mock library in models/__init__.py, as suggested in this blog post by @ManZzup https://medium.com/@manujith.nc/my-definitive-guide-to-getting-datastore-emulator-to-work-with-python-dbd3d49410c8

from google.auth.credentials import AnonymousCredentials

client = ndb.Client(project="test", credentials=AnonymousCredentials())