Documenting the current state of ScyllaDB as a Cassandra-compatible Backend

[andrii-kysylevskyi]

Is your feature request related to a problem? Please describe.
Temporal supports Cassandra as a storage backend, and ScyllaDB is often presented as a drop-in Cassandra alternative. It’s currently not mentioned in the documentation, and it's unclear whether using ScyllaDB with Temporal is recommended, unsupported, or simply unverified.

While looking into this, I found a few previous discussions that touched on ScyllaDB behaviour or compatibility questions:

• Temporal fails to create workflow with the same ID as previous one when Scylla is used as persistence #2683
• Add support for Yugabyte YCQL backend #3511 (comment)
• Possibly related: Corrupted history event when workflow args are too large #1267

This issue is mostly to clarify the current state and consolidate conversations in one place.

Describe the solution you'd like
Some clarification in the docs or guidance, such as:

• ScyllaDB is expected to work, but has not been officially tested, or
• Compatibility may be revisited in the future if there is interest.

No changes requested to core code right now - just a clearer direction for users evaluating storage options.

Describe alternatives you've considered

• Relying on scattered Slack/GitHub discussions.
• Community blog posts or notes (easy to get outdated).

Additional context
Opening this issue to track the topic and give a single reference point if ScyllaDB or Temporal contributors decide to explore this further. Happy to add more details if helpful. I would also be happy to add the note about ScyllaDB support (in whichever way the team prefers)

Thanks a lot in advance!