Cassandra chat memory schema initialisation fails on native protocol V4

Bug description

CassandraChatMemoryRepositoryConfig.ensureMessageTypeExist() executes its CREATE TYPE with a per-request keyspace:

SimpleStatement stmt = SchemaBuilder.createType(this.messageUDT)
    .ifNotExists()
    .withField(this.messageUdtTimestampColumn, DataTypes.TIMESTAMP)
    .withField(this.messageUdtTypeColumn, DataTypes.TEXT)
    .withField(this.messageUdtContentColumn, DataTypes.TEXT)
    .build();

this.session.execute(stmt.setKeyspace(this.schema.keyspace));

The driver permits a per-request keyspace only on native protocol V5 and above (DefaultProtocolVersionRegistry.supports, DefaultProtocolFeature.PER_REQUEST_KEYSPACE), so on a V4 connection the statement throws client-side before it reaches the server:

Failed to instantiate [org.springframework.ai.chat.memory.repository.cassandra.CassandraChatMemoryRepository]:
Factory method 'cassandraChatMemoryRepository' threw exception with message:
Can't use per-request keyspace with protocol V4

This makes the module's default configuration, spring.ai.chat.memory.repository.cassandra.initialize-schema=true, unusable against any server that negotiates V4.

Two secondary points:

• ensureMessageTypeExist() has no metadata guard, unlike ensureTableExists() and SchemaUtil.ensureKeyspaceExists(). It runs on every startup, so pre-creating the type does not avoid the failure. Setting initialize-schema=false and creating the schema by hand is the only workaround.
• SchemaBuilder already has a keyspace-taking overload, createType(String keyspace, String typeName), so the per-request keyspace is not needed.

Environment

Spring AI 1.1.8 and every release back to 1.0.0; the statement is byte-identical in 1.0.0, 1.0.3, 1.1.0, 1.1.2 and 1.1.8. Reproduced with java-driver-core 4.18.1 as managed by Spring Boot 3.4.13.

Steps to reproduce

Against any Cassandra 5.0 node with the session pinned to V4, standing in for Astra's ceiling:

DriverConfigLoader v4 = DriverConfigLoader.programmaticBuilder()
        .withString(DefaultDriverOption.PROTOCOL_VERSION, "V4")
        .build();

CqlSession session = CqlSession.builder()
        .addContactPoint(contactPoint)
        .withLocalDatacenter("datacenter1")
        .withConfigLoader(v4)
        .build();

CassandraChatMemoryRepository.create(CassandraChatMemoryRepositoryConfig.builder()
        .withCqlSession(session)
        .withKeyspaceName("test_ks")
        .build());

Expected behavior

Schema initialisation succeeds on V4. Qualifying the type in the statement rather than per request is protocol-agnostic:

SimpleStatement stmt = SchemaBuilder.createType(this.schema.keyspace, this.messageUDT)
    ...
this.session.execute(stmt);

With that change the same reproduction above creates the type, the table, and round-trips messages on V4. I have verified this locally and will open a pull request.

Start in CassandraChatMemoryRepositoryConfig.ensureMessageTypeExist(), then compare its schema initialization with ensureTableExists() and SchemaUtil.ensureKeyspaceExists(). Run the issue's session-pinned V4 reproduction; done means initialization creates the type and table and messages round-trip successfully without the per-request keyspace error.