Unsubmit Support (Resolves #271)

[jiachen247]

With reference to #271

Access Control

• Only avengers can unsubmit submissions by students belonging to their studio group.

Implementation:

• Introduced a new endpoint unsubmit
• Checks if submission status is submitted and if assessment is still open.
• then proceeds to rollback the status and the auto grading fields.

[coveralls]

Pull Request Test Coverage Report for Build 2438

• 31 of 34 (91.18%) changed or added relevant lines in 7 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 97.725%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/cadet_web/views/view_helpers.ex	3	4	75.0%
lib/cadet_web/controllers/grading_controller.ex	5	7	71.43%

Totals
Change from base Build 2434:	-0.3%
Covered Lines:	859
Relevant Lines:	879

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💛 - Coveralls

[indocomsoft]

Btw you should merge from master or rebase on master :)

[jiachen247]

okayss!! Will write test cases and rebase and i think we can try to merge this tmr if all goes well.

[martin-henz]

Is this PR ready to be merged?

[jiachen247]

Ok so for this, we/I just have to add

1. add a unsubmited_by and unsubmited_at to the submission table
   (we need to somehow make this information available on the frontend)
2. add tests

need to kiv password protected assessments, we shouldnt allow unsubmit for this.

[geshuming]

LGTM works fine on my end

:-(