Package Detail: Search/filter within related item lists (backend work)

As a librarian viewing a provider, package, or title record, I want to be able to filter the list of related items, so I can find a particular package or package-title.

When clicking the search icon next to the "Packages" or "Titles" headline, I should get a modal that contains the full search options normally found in the leftmost pane (minus the segmented control for Providers/Packages/Titles).

When the search modal is open:

• When entering a search string and submitting, the modal disappears and the list shrinks to only contain matching items.
• When solely clicking a filter, the modal stays open. It does not close until a submit event or the modal is dismissed. However, it does async fire off changes to the list behind the modal.

Prototype: details view component changes to pop open modal:
https://gist.github.com/cherewaty/ba1a050656476f2693020f5a246a5760

Not shown in attached GIF: modal should have a close icon to dismiss it.

Backend work

• add filters and targeted search options

Other requirements:

• Must display message when no results are returned (need to determine where this information should display)
• Must display error messaging (need to determine where this information should display)
• Display Sort option
  • Results should return in relevance order
• Results count should appear next to headline ("Titles" or "Packages") above list
• Search params should be in the url state
• Use the `stripes-components` `Modal` component (might need some responsiveness modifications)
• Focus should be set to the first result when the user closes the modal
• Modal should be accessible (confirm w/ JohnC. accessibility)