Add is_deliverable field to projects endpoint

[johnbradley]

Currently there is no way to tell if a duke-ds-project can be delivered. Add a is_deliverable field to the duke-ds-projects response and allow filtering via a query param. Partial list of things to consider for isDeliverable:

• deleted projects
• user must have admin privileges on the project
• if there is already an active delivery for a project

This is needed for https://github.com/Duke-GCB/datadelivery-ui/pull/21

[johnbradley]

I am second guessing preventing deliveries for projects that have active deliveries. A user might deliver a project to a user who is unresponsive to the email(vacation, etc). Because of this the user wants to deliver the project to a different recipient.

[dleehr]

I am second guessing preventing deliveries for projects that have active deliveries. A user might deliver a project to a user who is unresponsive to the email(vacation, etc). Because of this the user wants to deliver the project to a different recipient.

Yes, that's a use case, but if we create a second delivery for a project that's already in active delivery, what happens if someone accepts or declines on the original delivery?

Does that DukeDS API even allow the same project to be in two active deliveries? If it does, we'd want to cancel the original delivery first (and notify the original recepient)