Helper to start a discussion on the Open Food Facts wiki page of a username

[teolemon]

Why - Problem description

• Helper to add a discussion topic on the Open Food Facts wiki page of a username
• Integrate the Wiki with the app, especially the contribution dashboard, and create a proto social network using the mediawiki discussion page
• https://wiki.openfoodfacts.org/index.php?title=User_talk:Tacinte&action=edit&section=new
• The URL is 100% predictable from the username

[monsieurtanuki]

cf. #951 #955