Update controllers documentation

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

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

**Priority**: Low/Medium

Start by locating the controllers and handlers implementation; the issue does not identify specific files, entry points, or tests. Read how handlers currently process notifications and determine where configuration belongs. Done means handlers support configurable notifications with sensible defaults, as proposed.

Written by the indexing model from the issue text.