Add testing to User Services

[Coldboltage]

The aim is to add the first tests to Explorer Plus, so to make sure users are loaded correctly and the right information is given based on the user.

Acceptance Criteria

1) All lines of codes should be covered 2) Each test needs to evaluate the happy and all sad paths 3) Tests should fail via a mutation test

[Coldboltage]

Started on this. https://github.com/jmcdo29/testing-nestjs/tree/main/apps/complex-sample is being used to help create the standards of the test.