Document EF Core breaking changes and SaveChanges interceptor outcomes

[Copilot]

Fixes #4890
Fixes #4999
Fixes #4852

Several EF Core breaking changes and ISaveChangesInterceptor callback semantics were undocumented or misleading.

• EF Core 9 breaking changes

  • Document primitive collection API replacements.
  • Document SQL Server IndexOf null propagation and mitigation.

• SaveChanges interception

  • Clarify callbacks for failures, cancellations, and concurrency conflicts.
  • Update the auditing sample to record each outcome through the appropriate interceptor callback.

var indexes = context.Entities.Select(
    e => e.NullableString == null
        ? 0
        : e.NullableString.IndexOf(string.Empty));

[Copilot]

🟡 Changes recommended

Correct the interceptor version history and complete the primitive collection replacement guidance.

1 open finding

• Include reference-type replacement for ListComparer<TElement> · New

What changed in this PR

Documents EF Core 9 breaking changes and clarifies ISaveChangesInterceptor outcomes.

Changes:

• Documents primitive collection API replacements and SQL Server IndexOf behavior.
• Updates auditing callbacks for failures, cancellations, and concurrency conflicts.
• Clarifies interceptor callback semantics.

File	Description
samples/​core/​Miscellaneous/​SaveChangesInterception/​AuditingInterceptor.cs	Records failure, cancellation, and concurrency outcomes.
entity-framework/​core/​what-is-new/​ef-core-9.0/​breaking-changes.md	Documents EF Core 9 breaking changes.
entity-framework/​core/​logging-events-diagnostics/​interceptors.md	Clarifies SaveChanges callback semantics and examples.

🧠 Review effort: Lite

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[Copilot]

🔵 Needs a closer look

Preserve inner exception messages in the auditing sample and clarify nullable element-type guidance.

0 open findings

1 resolved since last review

• Include reference-type replacement for ListComparer<TElement>

🧠 Review effort: Lite