Allow configuration of piwik plugin using a configuration file

The default configuration options for piwik can not be overwritten by adding an entry in the configuration file indico.conf unlike the customizable settings for Indico.

I think it would be a nice to have, since it will allow having this configuration defined as code . The only working approach at this time is to set them manually through the UI.

Start by locating the Piwik plugin's configuration and how indico.conf is handled, then compare it with Indico's customizable settings. Confirm the expected configuration path and verify that values defined in indico.conf override defaults without requiring manual UI changes.

Written by the indexing model from the issue text.