Add unit tests around metadata & bundle checking

[ryanbourneuk]

Expected Behaviour

Metadata & bundle validation should have unit test coverage.

Current Behaviour

There is no unit test coverage.

Possible Solution

• Add #warnings around affected areas to direct where tests should be added.
• Add new tests to clear #warnings

Steps to Reproduce (for bugs)

Context

As part of the codable-refactor project, parts of the codebase (mainly storm object related) will be migrated from using manual JSON parsing / initialisation to using Codable. However, as ThunderCloud is used in many many apps, it'd be great for it to not break. If we determine the current state of ThunderCloud to be as expected, we can write a test suite against it - and then migrate to use Codable. The tests will then inform us if we have deviated from the expected behaviour.