Add unit tests for middleware

**Description**
Currently controllers lacks proper filtering support.

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

**Priority**: Low/Medium

Start by locating the middleware and controller entry points and checking how unit tests are organized. Determine where filtering belongs, which configurable options and sensible defaults are expected, and how controllers currently behave. Done means the filtering support is covered by unit tests and the default behavior is verified.

Written by the indexing model from the issue text.