CBG-5511: Stop db loading opting out of mobile collection if bootstrap migration is done

[gregns1]

CBG-5511

Stop loading/creating a db is bootstrap level migration is done for the bucket but the db is opted out of mobile collection

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

• https://jenkins.sgwdev.com/job/SyncGatewayIntegration/925/

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR adds a safety guard to prevent creating or loading databases without use_system_metadata_collection on buckets whose bootstrap metadata already resides in _system._mobile, avoiding cluster split-brain config states.

Changes:

• Reject DB create/load when the bucket bootstrap target is _system._mobile but the DB config is not opted into the system metadata collection.
• Introduce BucketBootstrapTargetIsSystemMobile on BootstrapConnection and implement it for Couchbase and Rosmar backends.
• Add regression tests covering both “migrated” and “opted-in-from-start” bucket scenarios.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
rest/server_context.go	Enforces opt-in requirement during DB load/add when bucket bootstrap target is _system._mobile.
rest/admin_api.go	Enforces opt-in requirement during DB creation before persisting config.
base/bootstrap.go	Extends BootstrapConnection with a method to resolve current bucket bootstrap target.
base/rosmar_cluster.go	Probes/caches registry location and exposes BucketBootstrapTargetIsSystemMobile for Rosmar.
db/database_error.go	Adds a new database error code/message for the opt-in-required case.
rest/metadatamigrationtest/metadata_migration_test.go	Adds tests ensuring non-opt-in DBs are rejected when bucket bootstrap metadata is in _system._mobile.