* Implement extensions and view support for LTI

* Add missing iss to token

* Add missing requirement, upgrade requirements

* Improving comment

* Add missing exception statement

* Update lti_consumer/lti_1p3/tests/extensions/rest_framework/test_authentication.py

Co-authored-by: Ned Batchelder <ned@nedbatchelder.com>

Co-authored-by: Ned Batchelder <ned@nedbatchelder.com>

This commit adds support for the LTI 1.3 Access token endpoint, as detailed in the IMS Security Framework.
The token is generated using the consumer's private key (stored in the XBlock) after validating the message sent by the LTI Tool using it's public key.

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

Features:
Implement LTI 1.3 launch support.
Add LTI 1.3 passthrough views as LMS plugins.