[TestSuite] Testing SDK function registration

Test the following scenarios in the function registration step:

- [ ] Register with non-existent endpoint
- [ ] Register non-serializable function (eg, a generator)
- [ ] Generic errors with reaching the web-service

Start by locating the SDK's function registration entry point and its existing tests, then run the relevant test suite. Add coverage for a missing endpoint, a non-serializable function such as a generator, and generic web-service errors; done means each scenario has clear, agreed assertions.

Written by the indexing model from the issue text.