Open filtered results from document view

Question from Jo Guldi:

> Some researchers will be curious about the ability to click through the speaker or date field from an individual source citation, i.e. from an individual speech, can I click on Benjamin Disraeli and search just his speeches, or just his speechess about democracy

#658 mentions something like this specifically for debates (where jumping to all speeches from a debate should also affect sorting).

For other fields with a search filter, such as speaker or party, there could be a link to add a filter on that field, i.e. to only see results where the field has that value.

I'm not sure whether the new search should include the current query and search filters, i.e. restrict the search further, or just show everything from that day/speaker/party/etc.

Either version could streamline users' workflow, but it would also clutter up the interface more.

Start at the document view and its speaker, date, and party search-filter entry points, then read issue #658 for the related debate behavior. Clarify whether a new filter preserves the current query and how sorting should work; done means the intended filtered-results workflow and interface behavior are agreed and implemented.

Written by the indexing model from the issue text.