[rfc] loadFirstByFieldEqualityConjunction, a convenience method

[ide]

Why

Several places (about five) in our codebase call loadFirstByFieldEqualityConjunction with { limit: 1 } either to get just the first row or to test for the existence of any matching row. The intent of the callers is often to get the latest row (limit 1, order by a descending timestamp). This PR adds a convenience method for that use case, primarily to help the callers convey their intent better, rather than saving one line of code by removing the need to specify limit: 1.

How

Added loadFirstByFieldEqualityConjunction to EntityLoader and EnforcingEntityLoader. This new method calls into loadManyByFieldEqualityConjunction and passes in limit: 1. It uses TS to prevent limit from being specified from the outside, which indicates a programming error. It also requires orderBy to be specified. We have a caller that doesn't care about order, just existence -- in this case, the caller should pass in orderBy: [] to explicitly show that it doesn't care about order. The more common pattern was to get the first row of an ordered set, though.

Test Plan

Added unit tests for both EntityLoader and EnforcingEntityLoader. Notably, the EntityLoader test ensures the privacy policy was evaluated only once even though two rows match, and also checks that the orderBy clause was honored.

[codecov]

Codecov Report

Merging #206 (2a2c2a2) into main (92f5529) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #206      +/-   ##
==========================================
+ Coverage   96.17%   96.18%   +0.01%     
==========================================
  Files          81       81              
  Lines        2065     2071       +6     
  Branches      269      271       +2     
==========================================
+ Hits         1986     1992       +6     
+ Misses         79       74       -5     
- Partials        0        5       +5     

Flag	Coverage Δ
integration	96.18% <100.00%> (+0.01%)	⬆️
unittest	96.18% <100.00%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
packages/entity/src/EnforcingEntityLoader.ts	100.00% <100.00%> (ø)
packages/entity/src/EntityLoader.ts	89.69% <100.00%> (+0.32%)	⬆️
...ty-example/src/adapters/InMemoryDatabaseAdapter.ts	45.83% <0.00%> (ø)

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[wschurman]

I think this sounds reasonable.