SOAP API client should have unit tests

[vlouvet]

The tests/test_soap_api.py file currently only has basic tests for initializing the client, but does not test any functionality beyond that.

It would be best if each function in soap_api/client.py had documentation added, and a unit test added.

With these tests added, we can start extending and testing functionality such as pagination and advanced SuiteQL queries (mentioned in a different issue).

[iloveitaly]

Agreed! Would love a PR for this.