fix: Encode id and className properties for nested non-ParseObjects

[cbaker6]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

Close #140

Approach

Since id and className are computed properties, they are not encoded by default and therefore can be removed from the ParseEncoder SkipKeys enum. Note that these keys should not be encoded manually if a developer decides to add their own custom encoding for ParseObjects or else the server may not handle their objects properly.

TODOs before merging

• Add tests
• Add entry to changelog

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.28%. Comparing base (173e7d8) to head (0d65c80).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #177      +/-   ##
==========================================
- Coverage   91.31%   91.28%   -0.04%     
==========================================
  Files         178      178              
  Lines       12073    12075       +2     
==========================================
- Hits        11025    11023       -2     
- Misses       1048     1052       +4     

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