Add support for nullable request/response

[viceroypenguin]

No description provided.

[Copilot]

Pull request overview

This PR aims to add support for nullable request/response types in the caching layer (and related handler usage), including a functional test case and a dependency update to a newer Immediate.Handlers version.

Changes:

• Relaxed ApplicationCache<TRequest, TResponse> generic constraints to allow nullable reference types (class?).
• Added a functional-test handler/cache pair that uses nullable request/response types.
• Updated Immediate.Handlers package version from 3.8.1 to 3.11.1.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
tests/Immediate.Cache.FunctionalTests/NullableTypesCache.cs	Adds a functional test handler/cache using nullable request/response types.
src/Immediate.Cache.Shared/ApplicationCache.cs	Updates generic constraints to allow nullable reference type arguments.
Directory.Packages.props	Bumps Immediate.Handlers dependency version.

[coveralls]

Coverage Report for CI Build 29757980199

Coverage decreased (-0.2%) to 94.017%

Details

• Coverage decreased (-0.2%) from the base build.
• Patch coverage: 1 uncovered change across 1 file (2 of 3 lines covered, 66.67%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
src/Immediate.Cache.Shared/ApplicationCache.cs	3	2	66.67%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	468
Covered Lines:	440
Line Coverage:	94.02%
Coverage Strength:	3.76 hits per line

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💛 - Coveralls

[viceroypenguin]

@coderabbitai review