Author: Sara Arjona
MDL-63692 core_group: Add group conversation messages to Privacy API
http://git.moodle.org/gw?p=moodle.git;a=commit;h=c752cce7dd1c655a5328339bbab520807c6f1e5d
http://github.com/moodle/moodle/commit/c752cce7dd1c655a5328339bbab520807c6f1e5d
+ 3.6 en [privacy:metadata:core_message,core_group]