CBG-5089: Add support for user defined metadata in diagnostic api

[RIT3shSapata]

CBG-5089

Describe your PR here...

• Added ability for user to pass the user defined xattrs into Sync Function Diagnostic API
• Added test coverage for the same

Pre-review checklist

• Removed debug logging (fmt.Print, log.Print, ...)
• Logging sensitive data? Make sure it's tagged (e.g. base.UD(docID), base.MD(dbName))
• Updated relevant information in the API specifications (such as endpoint descriptions, schemas, ...) in docs/api

Dependencies (if applicable)

• Link upstream PRs
• Update Go module dependencies when merged

Integration Tests

• GSI=true,xattrs=true https://jenkins.sgwdev.com/job/SyncGatewayIntegration/221/

[Copilot]

Pull request overview

This PR adds support for user-defined metadata (xattrs) in the Sync Function Diagnostic API, allowing users to test sync functions with custom xattr values. The changes enable passing user xattrs through the API request payload or reading them from existing documents in the database.

Changes:

• Added Meta field to SyncFnDryRunPayload to accept user-defined xattrs in API requests
• Updated SyncFnDryrun method signature to accept and process user metadata
• Changed userXattrKey() from private to public UserXattrKey() method across multiple files
• Added comprehensive test coverage for user xattr scenarios in diagnostic API

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
rest/diagnostic_doc_api.go	Added Meta field to payload struct and validation logic for user xattrs
rest/diagnostic_doc_api_test.go	Added test cases for user xattr handling and updated test setup for xattr support
db/crud.go	Updated SyncFnDryrun signature to accept userMeta parameter and apply it when provided
db/database_collection.go	Changed userXattrKey() to public UserXattrKey() method
db/database.go	Updated userXattrKey() call to UserXattrKey()
db/import.go	Updated userXattrKey() calls to UserXattrKey()
db/import_listener.go	Updated userXattrKey() calls to UserXattrKey()
db/change_cache.go	Updated userXattrKey() calls to UserXattrKey()
db/background_mgr_attachment_migration.go	Updated userXattrKey() call to UserXattrKey()

[bbrks]

Probably move the user xattr test cases to a test that is testing that specific sub-feature, so all the other tests can still run in CE mode.

[bbrks]

Need a bit more validation around the meta object being passed into the request really. See inline.

[bbrks]

This isn't ensuring there's nothing else set in the map (e.g. meta.foo)

I think that's mostly why I prefer the struct approach, though it also makes access easier since there's less type assertions too:

	Meta *SyncFnDryRunMeta `json:"meta,omitempty"`
}

type SyncFnDryRunMeta struct {
	Xattrs map[string]any `json:"xattrs,omitempty"`
}

We'd also need to length-check the Xattrs map to ensure only exactly 1 (matching) key is present as well - it's too easy to unintentionally pass extra data into the sync function otherwise that wouldn't be available in the real one.

e.g.

meta.xattrs[my_user_xattr_key]={"my_xattr_data":true}
meta.xattrs[bar]="buzz"

dry run could technically still be able to access meta.xattrs.bar despite not being available in a real sync function.

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

[Copilot]

Typo in field name: 'Xatrrs' should be 'Xattrs'.

Suggested change

	Xatrrs map[string]any `json:"xatrrs"`
	Xattrs map[string]any `json:"xattrs"`

[Copilot]

Typo in field name: 'Xatrrs' should be 'Xattrs'.

Suggested change

	Meta: SyncFnDryRunMetaMap{Xatrrs: map[string]any{"channelXattr": []string{"channel1", "channel3", "useradmin"}}},
	Meta: SyncFnDryRunMetaMap{Xattrs: map[string]any{"channelXattr": []string{"channel1", "channel3", "useradmin"}}},