feat(command): add FLUSHSLOTS command to clear keys in specified slot ranges in cluster mode

[sryanyuan]

Add FLUSHSLOTS command to clear keys in specified slot ranges in cluster mode

FLUSHSLOTS allows clearing keys from one or more cluster slots without affecting other slots.
It operates on the current connection's namespace (cluster mode does not support multiple namespaces).

The command returns an error if a slot migration is in progress to prevent conflicts.

Slot ranges can be specified as:
- Single slot: FLUSHSLOTS 1234
- Range: FLUSHSLOTS 100-200
- Multiple ranges: FLUSHSLOTS “0 2 4 6-9”

Example:
FLUSHSLOTS "0 2 4 6-9"

Unit tests have been added to verify clearing multiple slots and ensuring remaining keys match expectations.

[PragmaTwice]

Should it be a CLUSTERX subcommand, or at least in cmd_cluster.cc instead of cmd_server.cc?

[sryanyuan]

Should it be a CLUSTERX subcommand, or at least in cmd_cluster.cc instead of cmd_server.cc?

I agree — this command would be more appropriately placed under the CLUSTERX command as a subcommand, given that it relates to slot operations.

I will update the implementation accordingly.

Thank you for highlighting this.