Ensure correct LTI version of lti_user_id is used on launch

[donny-wong]

Proposed Changes

LTI launch from canvas is using LTI v1.1 for it's lti_user_id attribute. We need to use LTI v1.3 one as Roster sync uses this one, which is found under the subject attribute, "sub". LTI v1.1 and LTI v1.3 both have different values for lti_user_id.

If an instructor logs in from canvas and then does an Roster sync, other users who then launches from Canvas will get the following log error:

Couldn't find LtiUser with [WHERE "lti_users"."user_id" = $1 AND "lti_users"."lti_client_id" = $2 AND "lti_users"."lti_user_id" = $3] 

On production mode, they will see a 404 error on the browser but we will see the same error in the logs.

The reason this errors comes about is that when during the Launch, the following code is run in lti_deployments_controller.rb:

LtiUser.find_or_create_by(user: @real_user, lti_client: lti_client,
                              lti_user_id: lti_data[:lti_user_id])

It will first try to find this user, which they would not because of the different LTI versions, it would then try to create the user, but the DB would not allow it because of the unique index that requires User_id and lti_client_id combined has to be unique. So it would then raise the above error.

To test this locally:

1. Empty out lti_users table in DB
2. Launch from Canvas to MarkUs as an instructor
3. Do Roster sync
4. On Canvas, act as another user in that course and launch MarkUs
5. You will now be able to log in without the above error

...

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[coveralls]

Pull Request Test Coverage Report for Build 12112271970

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 91.758%

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Totals
Change from base Build 12107303502:	0.0%
Covered Lines:	41173
Relevant Lines:	44196

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💛 - Coveralls