Resolve "Indicate job offer sets 'Head TA' role instead of 'TA'"

Closes #192 (closed) Based on !357 (closed) What it does:

• Teacher can create HeadTA-only/TA-only/Either roles students can apply to.
• If teacher changes type of job offer, nothing happens, only when new people accept the job they will be given that new role.
• Promote/demote button only showed for "Either" type of job offers.
• Set defaults to "Either" type of job offers (since this is how it has been done before)
• Testing

added priolow + 1 deleted label

assigned to @dsavvidi

mentioned in merge request !357 (closed)

added 1 commit

• 654010ac - initial changes

Compare with previous version

added 1 commit

• 4645f261 - migrations

Compare with previous version

changed the description

marked the checklist item Teacher can create HeadTA-only/TA-only/Either roles students can apply to. as completed

marked the checklist item If teacher changes type of job offer, any students who have accepted the job get offered the job again (I assume we don't want to immediately promote/demote them right?) as completed

changed the description

added 1 commit

• b87aae58 - ta or headta offer type

Compare with previous version

changed the description

added 1 commit

• 6a9fb7d1 - final changes + testing

Compare with previous version

marked the checklist item Testing as completed

added 1 commit

• 1577e3db - change defaults

Compare with previous version

changed the description

marked this merge request as ready

added 64 commits

• 1577e3db...fbdf5289 - 63 commits from branch development
• 22635445 - Merge branch 'development' into 192-indicate-job-offer-sets-head-ta-role-instead-of-ta-2

Compare with previous version

added 6 commits

• 22635445...56f346dd - 5 commits from branch development
• 3c2464db - Merge branch 'development' into 192-indicate-job-offer-sets-head-ta-role-instead-of-ta-2

Compare with previous version

added 1 commit

• 849a769b - attempt

Compare with previous version

added 1 commit

• 936a0c7f - another attempt

Compare with previous version

requested changes

added 23 commits

• 936a0c7f...cfbfe74d - 21 commits from branch development
• d262142a - Merge branch 'development' into 192-indicate-job-offer-sets-head-ta-role-instead-of-ta-2
• cb71f121 - revert changes

Compare with previous version

changed the description

added 1 commit

• 9cb5d998 - spotless

Compare with previous version

added 1 commit

• 70ee750a - unnecessary tests

Compare with previous version

resolved all threads

added 4 commits

• 70ee750a...af121958 - 3 commits from branch development
• e7d9c6e2 - Merge branch 'development' into 192-indicate-job-offer-sets-head-ta-role-instead-of-ta-2

Compare with previous version

requested review from @rwbackx

approved this merge request

started a merge train

mentioned in commit 4a300df5

merged