Add unit tests for store

**Description**
Currently services lacks proper serialization support.

**Proposed solution**
Add configurable serialization with sensible defaults.

**Priority**: Low/Medium

No files or test paths are named. Start by locating the store and service implementation, then inspect existing unit-test conventions and current serialization behavior. Done means configurable serialization is supported with sensible defaults and the behavior is covered by unit tests.

Written by the indexing model from the issue text.