Feature: suggested finer grained user searching

[jbrown-xentity]

User Story

In order to improve search and secondary searches, data.gov users wants suggested ways to refine searching.

Acceptance Criteria

• [ ] GIVEN a user is trying to find data on a particular topic
  WHEN a search of that topic occurs
  THEN the search results are displayed
  AND alternative searches are proposed to further narrow the search

Background

@FuhuXia raised during a sprint discussion, everyone agreed this would be a much improved user experience. Also from that discussion: https://github.com/GSA/data.gov/issues/4649

Security Considerations (required)

None, using public search already.

Sketch

Unsure what parameters we could suggest for further filtering. We could suggest searching only the title title:search_term, or both the title and the notes field. We could suggest putting the whole search term in quotes to get the entire phrase. We could suggest adding tag, organization, or other filter, but we already do that on the left side (whether people use it is another story).

We should also define if there are circumstances where we do/don't show this information; ie only when the user search gives back > 1000 results? Always? Some other criteria?