Add an 'open' Support Call feature

Feature suggested by Christal:

Rather than having the following process for every interested grad student:

1. each interested grad student from other departments email the academic planner to get access,
2. academic planner adding them to the workgroup and giving them the instructional support role
3. inviting them to a support call
4. Grad student fills out form

It could instead be:

1. Create an 'open' support call
2. grad student fills out form (and is auto joined to the workgroup as instructional support)

While the open support call is open, anyone with a kerberos could log in, fill out the form, and then be 'auto joined' to the workgroup as instructional support.

Start by tracing the support call entry point and the form flow described in the issue, including how workgroup membership and the instructional support role are handled. Done means an open support call lets a user with a Kerberos login submit the form and be automatically joined to the workgroup with that role.