Fix truncating collections from MongoDB source database

[rkistner]

Specific scenario is when all of the following conditions are met:

1. We're replicating from an Atlas Flex instance.
2. There were changestream events recorded while the PowerSync service is paused.
3. We're only replicating from a single database.

Then we've observed an ns with for example {db: '67b83e86cd20730f1e766dde_ps'}, instead of the expected {db: 'ps'} on the change stream.

This caused issues on multiple levels internally:

1. We only used the collection name as the "relation_id" for the internal "source table" (bug 1).
2. The storage module then detected the equivalent of a renamed collection, since it saw the same relation_id, but a different schema.
3. We then truncate the table, but never did a snapshot of the "new" collection (bug 2).
4. This resulted in the collection being missing, apart from documents specifically updated again.

This fixes the issue on multiple levels:

1. Remove the relation_id for MongoDB source databases, and only rely on the db and collection names directly.
   1. This was simpler than consistently migrating the relation_id.
   2. We should probably do the same for MySQL, but that would require more testing.
   3. This means we can now correctly handle multiple collections of the same name in different dbs.
   4. This would avoid the "truncating" issue from above.
2. If we do see a new collection, snapshot it. While we don't expect this to happen, it will allow for more graceful handling of edge cases if we run into any again.
3. Implement a workaround for the incorrect ns from Flex instances.
4. Add proper logging for operations like truncating collections, for if we do run into scenarios like these again.

---

There is another report with similar symptoms, but not using a Flex instance. See this thread.

[changeset-bot]

🦋 Changeset detected

Latest commit: 58ee591

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 9 packages

Name	Type
@powersync/service-module-postgres-storage	Patch
@powersync/service-module-mongodb-storage	Patch
@powersync/service-module-mongodb	Patch
@powersync/service-core	Patch
@powersync/service-module-mysql	Patch
@powersync/service-module-postgres	Patch
@powersync/service-image	Patch
@powersync/service-core-tests	Patch
test-client	Patch

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[stevensJourney]

LGTM. Tested MongoDB locally and verified with a Flex instance.