Refactor light utils.go and include unit tests

[apoclyps]

What's Required?

At present, the light utils.go code is functional however the code could be greatly improved. Refactor the utilities as appropriate and include unit tests to cover the functionality provided by each function.

See: https://github.com/apoclyps/magic-home/blob/master/pkg/lights/utils.go

*Acceptance Criteria

• Must include tests