add version 2.0.3 changes which primarily involve adding expands

Description of the change

Adds the expands functionality, for certain API calls (refer to docs.merge.dev), you can add expand: ENUM_VALUE to change a flat id to a full sub object
Fields that are expanded are returned as merge_sdk.JSONValue type, if you wish to deserialize it to that type you can use the MODEL_NAMEFromJSON(raw_json_value) methods, i.e. CandidateFromJSON or EmployeeFromJSON
Miscellaneous backwards compatible model tweaks and additions
- i.e. adding avatar field to ticketing category user model

[ ] Bug fix (non-breaking change that fixes an issue)
[ ] New feature (non-breaking change that adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

[ ] The code changed/added as part of this pull request has been covered with tests, or the description above explains how testing was performed

[ ] This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or gif attached. Download "Kap" from the Mac App store for easy gif screen capture.