Swtich to external user id
Swtich to external user id

Signed-off-by: Giovanni Cimolin da Silva <bacb1eec935ad5e64ec871ac2543139b7d925d8f@gmail.com>

edx/xblock-lti-consumer,edx/xblock-lti-consumer,edx/xblock-lti-consumer,edx/xblock-lti-consumer