Add a "digital content" search option to the scope dropdown.

[ggeisler]

Part of #716, depends on #719.

When digital content is searchable

If an implementer has indexed the metadata (or even full text?) of the digital content associated with the archival components, that digital content could be searchable separately from the indexed content of the archival collections themselves. The UAlbany implementation is an example of this approach. This is an additional indexing challenge for implementers but seems like a good thing to do when feasible, as it gives users more powerful searching capability.

If digital content is searchable, the scope dropdown includes these options:

• everything
• all collections
• this collection
• digital content

The behavior for each:

Scenario A

The default option is "everything". This searches all collection content and all digital content.

Scenario B

If the user selects "all collections" and submits a query, only the EAD-based content is searched (i.e., what we currently do).

Scenario C

If the user selects "digital content" and submits a query, only the indexed digital content is searched.

Scenario D

If the user selects "this collection" and submits a query, both EAD-based and digital content is searched, but limited to content associated with the collection the user is currently within.

Scenario E

If there is no current collection selected (see #719) the "this collection" option is disabled.

Notes for further analysis

1. How are the combined search results presented? Albany's implementation uses a bento result. Alternative might be a combined result with a facet to separate.

2. How are digital search results different from current "Access = online" or "Online content" results, and how do we make this clear?

3. What would the fielded-search selection list include for digital content?

4. ...?