fix(di): cache registry factory execution

[thomhurst]

Summary

• execute each named typed/untyped registry factory exactly once under concurrent first resolution
• cache and rethrow factory construction failures consistently across registry, TryGet, and keyed DI paths
• define case-sensitive/empty-name and factory-failure contracts; add exact null guards
• reject unknown BackoffKind values instead of silently treating them as exponential
• add table-driven registry and configuration coverage, including all strategy sections and backoff kinds

Closes #25

Validation

• dotnet build Kevlar.slnx -c Release --no-incremental
• dotnet run --project tests/Kevlar.Tests -c Release --no-build -- --timeout 5m (352 passed)
• dotnet run --project tests/Kevlar.NetStandard.Tests -c Release --no-build -- --timeout 5m (1 passed)
• dotnet run --project tests/Kevlar.IntegrationTests -c Release --no-build -- --timeout 5m (16 passed)
• dotnet run --project tests/Kevlar.Analyzers.Tests -c Release --no-build -- --timeout 5m (19 passed)

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Review details

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📥 Commits

Reviewing files that changed from the base of the PR and between c3ffb96 and f4f7194.

📒 Files selected for processing (4)

• src/Kevlar.Extensions.DependencyInjection/IKevlarRegistry.cs
• src/Kevlar.Extensions.DependencyInjection/KevlarRegistry.cs
• src/Kevlar.Extensions.DependencyInjection/ShieldDefinition.cs
• tests/Kevlar.Tests/DependencyInjectionContractTests.cs

---

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[greptile-apps]

Greptile Summary

This PR makes named shield factory initialization concurrency-safe and caches both successful values and construction failures. It also validates unknown backoff enum values and adds DI/configuration contract coverage.

• Wraps cached registry factories in execution-and-publication Lazy instances.
• Applies exact null-name validation and documents naming and caching contracts.
• Rejects unsupported BackoffKind values instead of defaulting to exponential backoff.
• Adds concurrency, failure-caching, keyed-resolution, naming, registration, and configuration tests.

Confidence Score: 5/5

The PR appears safe to merge, with no actionable defects identified in the changed behavior.

The singleton registry and keyed-service paths share the same Lazy cache, ensuring one factory execution and a consistent cached value or exception, while the stricter backoff validation matches the stated contract.

Important Files Changed

Filename	Overview
src/Kevlar.Extensions.DependencyInjection/IKevlarRegistry.cs	Documents case-sensitive naming and the shared value-or-exception caching contract.
src/Kevlar.Extensions.DependencyInjection/KevlarRegistry.cs	Uses Lazy execution-and-publication semantics to ensure concurrent callers execute each factory once and share its outcome.
src/Kevlar.Extensions.DependencyInjection/ShieldDefinition.cs	Explicitly rejects undefined BackoffKind values rather than interpreting them as exponential.
tests/Kevlar.Tests/DependencyInjectionContractTests.cs	Adds broad contract coverage for concurrent DI resolution, cached failures, keyed paths, registration semantics, names, and configuration behavior.

Sequence Diagram

sequenceDiagram
    participant C1 as Concurrent caller 1
    participant C2 as Concurrent caller 2
    participant R as KevlarRegistry
    participant L as Cached Lazy
    participant F as Shield factory
    C1->>R: GetShield(name)
    C2->>R: GetShield(name)
    R->>L: GetOrAdd(key)
    R->>L: GetOrAdd(key)
    L->>F: Execute once
    F-->>L: Shield or exception
    L-->>R: Cached outcome
    R-->>C1: Same outcome
    R-->>C2: Same outcome

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