DOC-13648 document magma flusher threads 7.6

[ggray-cb]

Adds documentation for the Magma flusher settings to Couchbase 7.6.10.

The following changes link to a preview site. You will need the Docs Team credentials on Confluence.

• Added Magma Flushing and Compaction Threads to provide an overview of the settings. Also added a subsection above this to cover the existing description of reader and writer threads
• Added the new parameters to the Setting Thread Allocations REST API documentation. Also added missing sections to this documentation (such as the GET REST API method which wasn't there before).

Note: I've not added any sort of "What's New" entry for these settings because I don't think we want to call that much attention to them. Let me know if we should add some sort of announcement there.

[Copilot]

Pull request overview

This PR adds documentation for Magma flusher thread settings introduced in Couchbase Server 7.6.10, enabling administrators to configure thread allocation for Magma storage engine operations.

Changes:

• Added documentation for magma_max_default_storage_threads and magma_flusher_thread_percentage settings
• Enhanced REST API documentation with GET endpoint and comprehensive parameter descriptions
• Created reusable partial for common API parameters

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 12 comments.

File	Description
modules/rest-api/partials/user_pwd_host_port_params.adoc	New reusable partial defining standard REST API authentication and connection parameters
modules/rest-api/pages/rest-reader-writer-thread-config.adoc	Major expansion adding GET endpoint documentation and two new Magma thread configuration parameters
modules/learn/pages/buckets-memory-and-storage/storage-settings.adoc	New section documenting Magma flushing and compaction thread behavior and monitoring guidance
modules/learn/pages/buckets-memory-and-storage/storage-engines.adoc	Updated to reference new Magma thread tuning capabilities

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[t3rm1n4l]

We identified that we mistakenly added magma_max_default_storage_threads which is a duplicate of existing num_storage_threads setting. MB-70349 is opened to remove this parameter. Could you please wait until MB-70349 changes are merged? We have to rename magma_max_default_storage_threads back to num_storage_threads.

[ggray-cb]

We identified that we mistakenly added magma_max_default_storage_threads which is a duplicate of existing num_storage_threads setting. MB-70349 is opened to remove this parameter. Could you please wait until MB-70349 changes are merged? We have to rename magma_max_default_storage_threads back to num_storage_threads.

@t3rm1n4l I've updated the draft with the new setting.

[t3rm1n4l]

Looks good to me.

[sarahlwelton]

Some style pickiness. Couple typos. Some questions :)

[sarahlwelton]

Suggested change

	* See xref:learn:data/durability.adoc[Durability], for information about durable writes.
	* See xref:learn:buckets-memory-and-storage/storage-settings.adoc#threading[Threading] for an overview of threads.
	* For more information about durable writes, see xref:learn:data/durability.adoc[Durability].
	* For an overview of threads, see xref:learn:buckets-memory-and-storage/storage-settings.adoc#threading[Threading].

[sarahlwelton]

Though, really it's okay to just have these as bare links at the end of a section with no introductory text.

[sarahlwelton]

Thanks! LGTM 🚢