Author: Cameron Ball
MDL-35104 auth: Don't allow modification of username
Presently it is either unreliable, or not possible to change
the username of a user created with an authentication plugin.
In some cases it is even hard coded to fail. Ideally we would
sync the username, and the issue MDL-21928 exists to address
that. However, in the mean time we should not allow the
username of an external user to be modified.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=cbce72a73af57ddfdc720b39f8bad6380fb497ac
http://github.com/moodle/moodle/commit/cbce72a73af57ddfdc720b39f8bad6380fb497ac
+ 3.0 en [username,core_auth]
+ 3.0 en [username_help,core_auth]