Explain how to pass parameters to a message (#405)
Explain how to pass parameters to a message (#405)

- Added a note explaining that the severity of a message cannot be modified when overriding it.
- Implements #403.

Signed-off-by: Stefan Eike <bc738aff0c3bb36d5f83a68abbca8b364488f6fb@dometic.com>
dita-ot/docs