Migrate to using freezed package for immutability instead of equatable

[MoralCode]

This PR replaces equatable with freezed and also uses it to handle generation of JSON serialization and deserialization code

the sketchiest parts of this:

• I couldnt figure out why the automatic casing of the JSON keys wasn't working (was causing unit tests to fail because values like firstName werent getting populated), so i just manually set the necessary ones (i.e. the ones that are more than one word)
• Something was complaining about the fact that JsonKey shouldn't be used in the area where I used it, but since it solved the problem and couldn't figure out how better to do it based on the docs for the library. so i added top of file annotations to silence the warnings

The incomplete parts of this:

• the Results object has a couple JSON values that appear to be derived from existing values (date_utc, time_formatted, which seem like they could be derived from date and time, or the other way around, or combined into just a single DateTime value in dart). I haven't gotten around to figuring out how to make this part work yet.

Unit tests still pass with no changes made to them.

Will leave open a bit prior to merge to give an opportunity for feedback