Typecast enum values in Rest API Schema

[jakejackson1]

Description

Fix validation error when enum values are integers but the expected type is a string

Checklist:

• I've tested the code.
• My code is easy to read, follow, and understand
• My code follows the accessibility standards.
• My code has proper inline documentation / docblocks.

Additional Comments

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Project coverage is 77.82%. Comparing base (50e1283) to head (cc21c55).
Report is 4 commits behind head on development.

Files with missing lines	Patch %	Lines
src/Rest/Rest_Form_Settings.php	83.33%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           development    #1574   +/-   ##
============================================
  Coverage        77.82%   77.82%           
============================================
  Files              255      255           
  Lines            13896    13899    +3     
  Branches           370      370           
============================================
+ Hits             10814    10817    +3     
  Misses            3074     3074           
  Partials             8        8           

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