UserMailer#permissions_change_notification receives incorrect user

[nicolasfranck]

Please complete the following fields as applicable:

What version of the DMPRoadmap code are you running? (e.g. v2.2.0)

3.0.2

Expected behaviour:

The mail template that is sent to user whose permissions have been
changed should be addressed to that user, not to the user that changed
it.

Actual behaviour:

It addresses the user that changed it.

RolesController#update supplies the current_user as second argument to UserMailer.permissions_changed_notification, so @username = user.name becomes the name of the user that made the change.

Should be @username = role.user.name? And maybe rename the second argument to current_user to make
it clear what that argument is for.