Convert is_past_due to a method

This is just to keep it in line with other xblocks that define
an is_past_due attribute. Nicer if they all have the same access
pattern.

[BD-29] [TNL-6993] [BB-2706] Make LTI Consumer indexable

BOM-1953 : Replace pycryptodome with pycryptodomex

[BD-18] remove nose footprints from the project

Merge pull request #87 from open-craft/patrick/BB-2516-lti-improvements-implement-context-claim-on-lti

[BD-24] [TNL-7316] Implement context claim on LTI 1.3

[BD-2] [BB-2612]: Add ADR to define LTI Plugin architecture implementation

Removed usages of package six

Find all packages in setup.py

Merge pull request #77 from open-craft/patrick/BB-2523-add-support-for-lti-embeds-in-the-course-tabs-a

BD-02 BD-03 Add support for LTI embeds in course tabs and elsewhere

Include new packages in distribution

Renamed module to avoid import confusion

Removed deprecated future imports

[BD-2] BB-2365: Merge LTI 1.3 support to master. 

k# Please enter the commit message for your changes. Lines starting

Also fixes a few untreated exceptions and remove unused variables.

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

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