feat: Teaching Assistant role [BB-8580][QUINCE] #389

Job	Run time
collect-and-verify (3.8, pinned)	5m 6s
gh-hosted-python-3.8,django-pinned,lms-1	13m 54s
gh-hosted-python-3.8,django-pinned,lms-2	10m 39s
gh-hosted-python-3.8,django-pinned,lms-3	19m 24s
gh-hosted-python-3.8,django-pinned,lms-4	24m 54s
gh-hosted-python-3.8,django-pinned,lms-5	12m 27s
gh-hosted-python-3.8,django-pinned,lms-6	17m 16s
gh-hosted-python-3.8,django-pinned,openedx-1	16m 33s
gh-hosted-python-3.8,django-pinned,openedx-2	17m 24s
gh-hosted-python-3.8,django-pinned,openedx-3	10m 20s
gh-hosted-python-3.8,django-pinned,openedx-4	7m 27s
gh-hosted-python-3.8,django-pinned,cms-1	5m 25s
gh-hosted-python-3.8,django-pinned,cms-2	18m 26s
gh-hosted-python-3.8,django-pinned,common-1	12m 20s
gh-hosted-python-3.8,django-pinned,common-2	6m 38s
gh-hosted-python-3.8,django-pinned,xmodule-1	8m 8s
	3h 26m 21s

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