Add Unit Objects

[joncameron]

Description

Adding Units as objects in Avalon: model scaffolding to start building the Unit in Avalon.

Unit Metadata

• Title
• Description
• Poster Image
  • Poster Image alt text (new; to be added to the Unit, rather than as an attribute of the poster image)
• Contact Email
• Website URL
• Website Label
• Staff Roles
• Special Access Roles

Note on Indexed File and poster image alt text

There is an "indexed file" category that we could use to add the alt text to poster images, but this could also come after this work on adding the Unit object.
With adding stuff to Indexed File, if we move stuff out of Fedora and into Active Storage it would make sense to target that. We want to avoid putting stuff into Fedora that we're just going to move out.

Done Looks Like

• Create model class
• Create controller
• Create views associated with controller (see Unit Admin Page #6055)