fix(filter)!: use a constant for a TimeOnly value on net6.0

[pdevito3]

For later consideration in a major version. Do not merge now. #134 restored the v1.14.2 behavior to keep v1.x compatible (restore commit 7653edb). This PR re-applies the net6.0 part of 5db8c4b (#110). The captain decides on this PR separately.

Summary

-    private static Expression NewTimeOnly(TimeOnly time)
+    private static Expression? NewTimeOnly(TimeOnly time)
     {
-        var ctor = typeof(TimeOnly).GetConstructor(new[] { typeof(int), typeof(int), typeof(int), typeof(int), typeof(int) })!;
+        var ctor = typeof(TimeOnly).GetConstructor(new[] { typeof(int), typeof(int), typeof(int), typeof(int), typeof(int) });
+        if (ctor == null)
+        {
+            return null;
+        }

When the constructor does not exist, FilterValue.Literal uses Expression.Constant for the value.

v1.14.2 behavior (and main)

QueryKit builds a TimeOnly value with new TimeOnly(int, int, int, int, int). This constructor (with microseconds) came in .NET 7. On net6.0 the lookup returns null, and Expression.New throws ArgumentNullException. Every filter with a TimeOnly value fails on net6.0. The opt-in ParameterizeFilterValues path does not use this code.

New behavior

On net6.0, the value is a constant TimeOnly. On net7.0 and later, nothing changes.

Example

// net6.0
FilterParser.ParseFilter<TestingPerson>("""Time == "08:30:00" """);

• v1.14.2 and main: throws ArgumentNullException.
• This PR: the filter compares x.Time with a constant TimeOnly value of 08:30:00.

Justification

QueryKit targets net6.0, but a TimeOnly filter does not work there. A constant value is correct for in-memory queries and for EF Core.

Migration

None. A net6.0 caller that caught ArgumentNullException for a TimeOnly filter now gets results.

README

No change.

Tests

PR 134 changed no test for this item. The test projects run only on net10.0, and this machine has no net6.0 runtime, so no test can run the net6.0 path. dotnet build -f net6.0 of the library has 0 warnings and 0 errors.

dotnet test: 470 unit tests and 297 Postgres integration tests (Testcontainers) pass, 0 failures.

Rebase on main

This branch is rebased on current main (#169). The rebase had no conflicts. The breaking change did not change.