Implement CassandraChatMemory

[michaelsembwever]

And, fix initialize-schema docs and so that it actually works.

In action here: https://github.com/datastax/ai-agent-java/blob/mck/step-1-new-chat-model/src/main/java/com/datastax/ai/agent/history/AiAgentSession.java

[tzolov]

This is really cool! Thanks @michaelsembwever

Let me know if stumble on some design flows with simplistic ChatMemory interface.

[michaelsembwever]

@tzolov ready for review.

Second commit is refactoring of CommonVectorStoreProperties to what i believe is a better package location.

[tzolov]

Thanks @michaelsembwever
LGTM. you've forgotten to add the CassandraAutoConfiguration to the AutoConfiguration.imports. But I will fix it during the merge.

FYI, after M2, we will explore how to implement a "generic" Spring Data Chat Memory support that might affect your impl. as well.
Anyway, this is the first persistent chat memory implementation! :)

[tzolov]

Rebased, squashed and merged at 4aacab0