Miscellaneous bug fixes

[gwynne]

These changes are now available in 1.48.5

This update contains the following fixes and changes:

• Logging (especially of Fluent queries) is now done in structured fashion using metadata, as recommended for logging in libraries.
• Several superfluous Sendable workarounds have been removed (they were never needed).
• Resolved several DocC warnings.
• When using eager loading with @CompositeChildren properties, specifying withDeleted: true now works (previously the flag was ignored).
• query.aggregate(.custom(.sql(...))) now works correctly (previously only plain strings were handled for custom aggregates)
• Fixed a FluentBenchmarks test so that it actually tests what it claims to.
• Fixed numerous FluentBenchmarks tests so they no longer crash if something goes wrong during migrations.
• ISO8601TimestampFormat now correctly respects the milliseconds setting on a case-by-case basis when used in both modes in the same application (the behavior was previously nondeterministic).

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 16.60900% with 241 lines in your changes are missing coverage. Please review.

Project coverage is 24.74%. Comparing base (cb91bf9) to head (6554e35).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #610 +/- ## ========================================== - Coverage 25.02% 24.74% -0.28% ========================================== Files 149 149 Lines 8593 8648 +55 ========================================== - Hits 2150 2140 -10 - Misses 6443 6508 +65 ``` | [Files](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor) | Coverage Δ | | |---|---|---| | [Sources/FluentBenchmark/FluentBenchmarker.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentBenchmark%2FFluentBenchmarker.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRCZW5jaG1hcmsvRmx1ZW50QmVuY2htYXJrZXIuc3dpZnQ=) | `0.00% <ø> (ø)` | | | [...urces/FluentBenchmark/Tests/PerformanceTests.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentBenchmark%2FTests%2FPerformanceTests.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRCZW5jaG1hcmsvVGVzdHMvUGVyZm9ybWFuY2VUZXN0cy5zd2lmdA==) | `0.00% <ø> (ø)` | | | [...rces/FluentKit/Concurrency/Model+Concurrency.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentKit%2FConcurrency%2FModel%2BConcurrency.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRLaXQvQ29uY3VycmVuY3kvTW9kZWwrQ29uY3VycmVuY3kuc3dpZnQ=) | `25.00% <ø> (ø)` | | | [Sources/FluentKit/Properties/CompositeID.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentKit%2FProperties%2FCompositeID.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRLaXQvUHJvcGVydGllcy9Db21wb3NpdGVJRC5zd2lmdA==) | `87.50% <100.00%> (ø)` | | | [Sources/FluentKit/Properties/Group.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentKit%2FProperties%2FGroup.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRLaXQvUHJvcGVydGllcy9Hcm91cC5zd2lmdA==) | `68.25% <100.00%> (ø)` | | | [Sources/FluentKit/Properties/ID.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentKit%2FProperties%2FID.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRLaXQvUHJvcGVydGllcy9JRC5zd2lmdA==) | `80.00% <100.00%> (-1.09%)` | :arrow_down: | | [Sources/FluentKit/Properties/OptionalField.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentKit%2FProperties%2FOptionalField.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRLaXQvUHJvcGVydGllcy9PcHRpb25hbEZpZWxkLnN3aWZ0) | `83.07% <100.00%> (-0.51%)` | :arrow_down: | | [Sources/FluentKit/Properties/Timestamp.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentKit%2FProperties%2FTimestamp.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRLaXQvUHJvcGVydGllcy9UaW1lc3RhbXAuc3dpZnQ=) | `84.88% <100.00%> (ø)` | | | [...ry/Builder/QueryBuilder+Join+DirectRelations.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentKit%2FQuery%2FBuilder%2FQueryBuilder%2BJoin%2BDirectRelations.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRLaXQvUXVlcnkvQnVpbGRlci9RdWVyeUJ1aWxkZXIrSm9pbitEaXJlY3RSZWxhdGlvbnMuc3dpZnQ=) | `100.00% <ø> (ø)` | | | [Sources/FluentKit/Schema/DatabaseSchema.swift](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree&filepath=Sources%2FFluentKit%2FSchema%2FDatabaseSchema.swift&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor#diff-U291cmNlcy9GbHVlbnRLaXQvU2NoZW1hL0RhdGFiYXNlU2NoZW1hLnN3aWZ0) | `54.54% <ø> (ø)` | | | ... and [42 more](https://app.codecov.io/gh/vapor/fluent-kit/pull/610?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=vapor) | |