Develop workflow and necessary features for handling content which should not be made available online

[helrond]

Is your feature request related to a problem? Please describe.

Although potentially outside the scope of this application, we need to define a process for handling digitized content which should not be made available online immediately.

Describe the solution you'd like

A solution needs to be thought through and proposed. This will likely result in filing other issues, some of which may be on other apps/repositories.

Additional context

Things to consider:

• How restrictions are expressed and articulated in the data pipeline (Pisces)
• Where checking for embargoed content is done (in this app or before)
• How the length of the embargo period for materials affects the approach to where they are stored