Create indicators for consortial/institutional buy-ins

[SteelWagstaff]

There are many different purchase permutations for consortial networks. Central networks may have purchased one type of plan with central book/user limits and a specific start/renewal dates, and individual institutions may have purchased buy-ins with different book limits and separate start/renewal dates.

Super admins (i.e. Pressbooks staff) need to be able to update and see the contract renewal dates for consortia and individual members, and edit and view the book/user limits for both central networks and individual institutions to match their contractual values.

If a central network has purchased unlimited access for all member institutions, book/user limits for both the consortia and its member institutions should be irrelevant. In addition, network managers should be able to add institutional managers for any/all institutions in the network.

If a central network has not purchased unlimited access, the central network should be able to have an assigned book and user limit (entered by a super admin). Usage towards the consortia limits should be calculated by summing all of the unassigned books/users along with the books/users assigned to institutions which have not purchased individual buy-in to the network.

One way to do this might be to add an 'unlimited' checkmark at the network level, along with book and user limits for the network. This could be a new settings page only visible to super admins (similar to the whitelabel settings or Google Analytics settings pages) or it could be new fields added to the existing network settings page.

If an individual network has bought in (i.e. purchased access to the network), a super admin should be able to indicate that that institution has bought in to the network. They should then be able to set a book limit and/or user limit for that institution. Super admins and network managers should be able to assign/remove institutional managers for institutions which have purchased buy-ins.

We should also add a display column that shows whether or not an institution has bought into the network to the institution list page and the renewal date for their deal. Probably a buy-in column (that displays a check mark) and a renewal date column?

See https://docs.google.com/document/d/1K637TC99kL7Zd0mTgGiv7qDg0H4VZVMDzU_chmy5C1Y/edit?usp=sharing

See https://docs.google.com/document/d/1wdjQsImrKEIAzhqF9onm1ATUDRAN99yFMS21Jr7kuVw/edit and https://docs.google.com/document/d/1nQAlIpbg-32bnXuBB-Djl1ZJHXRGSn-y6K34ZrWMYjQ/edit for details about requirements & current consortial arrangements.

[MichelleWeremczuk]

Wireframe WIP

[SteelWagstaff]

Superceded by #61