fix(@aws-amplify/datastore-storage-adapter): SQLiteAdapter fails on required related models

[svidgen]

Description of changes

Adding manyToMany tests revealed that the SQLiteAdapter was failing to handle required related models correctly. As it was loading from the database, the adapter was attempting to initialize records with null values for the required related-model fields, rather than allowing these fields to be lazy-loaded using the given FK's. This was causing operations against models with required belongsTo and hasOne fields to throw errors, due to the fields being initialized null.

I'm not completely sure why these fields are present in the SQLite schema to begin with, so I'm leaving them in for now. However, this change fixes the issue by filtering related model fields out of the initialization entirely. Only the FK's should be populated.

Issue #, if available

#10718

Description of how you validated changes

Added unit tests. Red/Green'd the tests.

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

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

[iartemiev]

LGTM 👍🏻

[codecov-commenter]

Codecov Report

Merging #10720 (6c2ed2d) into main (def0154) will increase coverage by 0.05%.
The diff coverage is 97.36%.

@@            Coverage Diff             @@
##             main   #10720      +/-   ##
==========================================
+ Coverage   85.65%   85.71%   +0.05%     
==========================================
  Files         196      196              
  Lines       18261    18335      +74     
  Branches     3892     3900       +8     
==========================================
+ Hits        15642    15715      +73     
- Misses       2543     2544       +1     
  Partials       76       76              

Impacted Files	Coverage Δ
packages/datastore/__tests__/commonAdapterTests.ts	98.16% <97.26%> (-0.17%)	⬇️
packages/datastore/__tests__/helpers.ts	84.24% <100.00%> (+0.10%)	⬆️
packages/datastore/src/storage/relationship.ts	93.67% <0.00%> (+1.26%)	⬆️

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