Saga not found handler updates

[danielmarbach]

This PR documents the changes introduced in Particular/NServiceBus#7516 for NServiceBus v10

Instead of using the interface name all over the place, we are now using the concept, which avoids having to duplicate countless pages.

[danielmarbach]

I simply made this v10 snippet larger, also containing the registration. To not overwhelm the page with too much noise, I moved the region inside the ConfigureHowToFindSaga method. I figured doing a partial in the page for the snippet to add another sentence seems to be overkill.

[DavidBoike]

I hate split snippets but I get it. I wish we had some sort of #region snippet-ignore that turned multiple lines into ...

[Copilot]

Pull request overview

This PR updates the documentation to reflect changes introduced in NServiceBus v10 regarding saga not found handlers. The key change is moving from interface-specific terminology (IHandleSagaNotFound) to the conceptual term "saga not found handler" throughout the documentation, which improves consistency and reduces duplication across multiple pages.

Key changes:

• Replaces references to IHandleSagaNotFound interface with the conceptual term "saga not found handler" across all documentation
• Documents the new ISagaNotFoundHandler interface and registration approach for v10 (no longer auto-registered via assembly scanning)
• Updates code snippets to demonstrate the new ConfigureNotFoundHandler<T>() mapping API

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tutorials/nservicebus-sagas/3-integration/tutorial.md	Updates tutorial text to use "saga not found handler" terminology
nservicebus/upgrades/9to10/index.md	Documents the migration from IHandleSagaNotFound to ISagaNotFoundHandler with mapping examples
nservicebus/sagas/saga-not-found_multiple-sagas_core_[10,).partial.md	New partial file for v10+ (currently empty)
nservicebus/sagas/saga-not-found_multiple-sagas_core_[,10).partial.md	New partial file documenting multiple saga behavior for pre-v10
nservicebus/sagas/saga-not-found.md	Updates main saga not found documentation to use conceptual terminology
nservicebus/sagas/index.md	Updates index page references to use "saga not found handler" terminology
nservicebus/sagas/analyzers_not-found-handler_core_[10,).partial.md	New partial file with analyzer documentation for v10+
nservicebus/sagas/analyzers_not-found-handler_core_[,10).partial.md	New partial file with analyzer documentation for pre-v10
nservicebus/sagas/analyzers.md	Updates analyzer documentation to use conceptual terminology with partials
Snippets/Core/Core_10/Sagas/SagaNotFoundHandler.cs	Adds code snippet demonstrating ISagaNotFoundHandler usage and configuration
Snippets/Core/Core_10/Core_10.csproj	Bumps NServiceBus package version to 10.0.0-alpha.21

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[DavidBoike]

I hate split snippets but I get it. I wish we had some sort of #region snippet-ignore that turned multiple lines into ...

[danielmarbach]

Merging for now. We can also do more edits if necessary