Fixture auth_dict returned both a header and a token, the latter was
discarded in most tests. The specific userN_auth fixtures only returned
the header. To simplify, those fixtures are replaced with just
auth_headers for most cases, and upload_tokens for the few cases where
the token is needed.

- Use utils create_convert for groups
- Remove unnecessary fixtures
- Shorten user_groups* to groups*

- test users -> userN
- test user groups -> groupOMN
- test auth -> auth

- Rename test_user_groups_dict -> ~_group_molds
- Add test_user_molds (user_label: user_dict)
- Remove unused imports from conftest

Squashed commits:
* Add group router tests
* Add test example groups
* Add test get single group
* Add test get invalid group
* Extend user group fixtures
* Add test delete user group
* Add test update user group
* Add test get single group upload
* Integrate group upload tests
* Add test get group uploads