datastore: separate interface from implementation

[Mohammad-nassar10]

Problem Statement

The current datastore.go includes the interface and the implementation of in-memory datastore in the same file.

Proposed Solution

Split pkg/datastore/datastore.go into types.go (interface) and memory.go (in-memory implementation) so a different implementation of the datastore (like Redis-backed store) can be added later.

Alternatives Considered

No response

Willingness to Contribute

Yes, I can submit a PR

Additional Context

No response

[Mohammad-nassar10]

/assign