fix: use NetworkTopologyStrategy for keyspace creation to support ScyllaDB 2026.x

[nikagra]

Fixes #191.

Problem

ScyllaDbSinkConnector.java hardcodes SimpleStrategy when creating the connector keyspace. ScyllaDB 2025.4+ enables tablets by default for all user keyspaces, and tablets require NetworkTopologyStrategy — SimpleStrategy is outright rejected with:

InvalidConfigurationInQueryException: SimpleStrategy doesn't support tablet replication

This causes the connector to fail at startup whenever scylladb.keyspace.create.enabled=true is used against ScyllaDB 2025.4+. It is also the root cause of the CI failures in PR #167.

Fix

One-line change: replace "SimpleStrategy" with "NetworkTopologyStrategy" in the withReplicationOptions call.

NetworkTopologyStrategy accepts replication_factor as a shorthand (ScyllaDB docs) that auto-expands to all datacenters in the cluster. No DC name is required — the existing config.keyspaceReplicationFactor continues to be honoured as-is.

Backwards Compatibility

• The IF NOT EXISTS clause means existing keyspaces are not affected.
• NetworkTopologyStrategy with the replication_factor shorthand is supported by ScyllaDB (all versions) and Cassandra 4.0+.
• The connector's tables have no counters, secondary indexes, or materialized views, so they are fully tablet-compatible without any tablets = {'enabled': false} workaround.