This is a new activity module, Simple Certificate, based on certificate module maintained by Mark Nelson, but simpler, no needs to change any code to add a new certificate format, and moodle's administrator don't need to upload image files.
The certificate text are full customizable, using special text marks that will be replaced by variables (like student name, course name, grade, ...), don't need to change any language file.

https://github.com/bozoh/moodle-mod_simplecertificate