Add unit tests for services

**Feature request**
It would be great to have serialization for types.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_serialization` with default `false`.

The issue names no files, tests, or entry points. First clarify which types need serialization, where configuration is defined, and which services are in scope; then identify the existing service tests and configuration tests. Done should include a documented default for enable_serialization and coverage proving the intended serialization behavior.

Written by the indexing model from the issue text.