Make dialog_confirm_spam_message a plurals string key only to match 72870174cea1321dc2658c796fae52805319b9bd.
The actual pluralization still has to be done.
Update issue 1916
Status: started
I updated the existing strings.xml with many of your fixes and added a Canadian French specific strings.xml: it only contains terms that differ.
Identified terms (fr / fr_CA) :
e-mail / courriel
spam / pourriel
You can now choose "Français (Canada)" language from the configuration screen.
I tried to match the Gmail application running on a system configured with French locale: it mainly use the "message" term and sometime "e-mail" like in notifications as well as "spam".
Some other modifications are spelling fixes.