Allow users to define their own Vector DB as their cache

[ishaan-jaff]

Allow users to define their own Vector DB for the Cache. For compliance reasons users want the ability to define their own vector DB as cache

cc @grski

[grski]

@hkorzeniewski for tomorrow fyi

[grski]

For now we do not need vectorDB as we r doing simply an exact match with the cache - this is implemented here:#33
In the future next steps will include proper vector store/db and semantic similarity matches.