[4.0.3 backport] CBG-5076: remove serialisation from caching process

[torcolvin]

[4.0.3 backport] CBG-5076: remove serialisation from caching process

cherry-pick of 9a42542

[Copilot]

Pull request overview

This PR removes serialization from the channel caching process by eliminating the pre-computed serialization string from the channels.ID type. The change simplifies the channel ID representation and removes the dependency on string-based key matching in the change listener.

Changes:

• Modified channels.ID to remove the serialization field and update its String() method to return only the channel name
• Updated changeListener to use channels.ID directly as map keys instead of strings
• Adjusted test expectations to reflect the simplified string representation of channel sets

Reviewed changes

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

File	Description
channels/set.go	Removed serialization field from ID struct and simplified String() method to return only channel name
db/change_listener.go	Changed keyCounts map and related methods to use channels.ID instead of string keys, added collection ID constant for principal documents
channels/set_test.go	Updated test expectations to match new string representation without collection ID prefix

[Copilot]

The comment warns about logging implications but doesn't specify what "context on the log line" means. Consider clarifying what context is expected to provide the collection ID information, or provide an example of proper usage.

Suggested change

	// String returns the channel name as a string, omitting the collection ID, so beware when using for logging purposes
	// that the collection name is logged from the context on the log line
	// String returns only the channel name, and intentionally omits the collection ID.
	// When using this in log messages, always include the collection identifier separately in the
	// log context or format string (for example: "collection %d channel %s").

[Copilot]

The comment should explain why collection ID 0 is used for principal documents and whether this is a special/reserved value. This magic number would benefit from additional context about its significance.

Suggested change

	// principalDocCollectionIDForChannelID is the collection ID for construction of channel ID for principal documents (users, roles).
	// principalDocCollectionIDForChannelID is the (synthetic) collection ID used when constructing
	// channel IDs for principal documents (users, roles). Principals are global and are not stored
	// in a normal data collection, so they are associated with this reserved collection ID (0) only
	// for the purposes of channel identification. This value must not overlap any real collection ID.