fix(datastore): Enable subscription selection set to contain required fields only

[royjit]

Issue #

Description

Enable a feature to create custom selection set with only primary key. This will allow mutation happening in other devices with custom selection set to be synced without error in Amplify Swift v1. The logic takes parts from the Amplify Swift v2 PR - #2658

General Checklist

• Added new tests to cover change, if needed
• Build succeeds with all target using Swift Package Manager
• All unit tests pass
• All integration tests pass
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Documentation update for the change if required
• PR title conforms to conventional commit style
• New or updated tests include Given When Then inline code documentation and are named accordingly testThing_condition_expectation()
• If breaking change, documentation/changelog update with migration instructions

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Merging #3016 (6becf66) into v1 (648e4c7) will decrease coverage by 0.01%.
The diff coverage is 82.35%.

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@@            Coverage Diff             @@
##               v1    #3016      +/-   ##
==========================================
- Coverage   63.82%   63.82%   -0.01%     
==========================================
  Files         722      722              
  Lines       23142    23181      +39     
==========================================
+ Hits        14771    14795      +24     
- Misses       8371     8386      +15     

Flag	Coverage Δ
API_plugin_unit_test	62.90% <ø> (-0.09%)	⬇️
AWSPluginsCore	73.24% <88.60%> (+0.13%)	⬆️
Amplify	51.16% <0.00%> (-0.06%)	⬇️
Analytics_plugin_unit_test	72.58% <ø> (ø)
Auth_plugin_unit_test	83.80% <ø> (ø)
DataStore_plugin_unit_test	81.12% <ø> (ø)
Geo_plugin_unit_test	57.87% <ø> (ø)
Predictions_plugin_unit_test	33.58% <ø> (ø)
Storage_plugin_unit_test	59.53% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...Model/Internal/Schema/ModelField+Association.swift	43.68% <0.00%> (-2.71%)	⬇️
...re/Model/GraphQLDocument/GraphQLSubscription.swift	81.81% <50.00%> (ø)
.../Model/Decorator/ConflictResolutionDecorator.swift	81.81% <77.41%> (-8.81%)	⬇️
...hQLDocument/ModelBasedGraphQLDocumentBuilder.swift	96.15% <100.00%> (+0.69%)	⬆️
...aphQLRequest/GraphQLRequest+AnyModelWithSync.swift	89.84% <100.00%> (+0.07%)	⬆️
...re/AWSPluginsCore/Model/Support/SelectionSet.swift	98.11% <100.00%> (+0.19%)	⬆️

... and 2 files with indirect coverage changes

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