Update handlers documentation

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

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

**Priority**: Low/Medium

Start by locating the handlers implementation and any existing serialization entry points or tests; the issue does not name specific files. Confirm the supported handler data and sensible defaults before implementing configurable serialization. Done means the configuration works with documented defaults and the relevant tests pass.

Written by the indexing model from the issue text.