added public_name search function

[biskwikman]

closes #2082

I basically mimicked the structure of the code for usernames, but pointed the new query to the public_name column of the participants table, it seems to work fine.

[Changaco]

I think it's probably better to have a single query and unified results section for both usernames and public names.

Also, a new trigram index is needed on the public_name column to speed up the search:

CREATE INDEX public_name_trgm_idx ON participants
    USING GIN (lower(public_name) gin_trgm_ops)
    WHERE status = 'active'
      AND public_name IS NOT null;

[biskwikman]

Should we include the username and public name under the avatar on all search results from now on? I think it would help with any confusion if an account has a similar username and public name.

[Changaco]

Yes, both names should be displayed for all results.

[biskwikman]

I've made it so the username and public name are returned in a single query, and both are displayed. I also added the index.

I'm not sure what word to use instead of "username" now. For example in the phrasing "Found a matching username". I was thinking of just using "user", but maybe "individual" would be more consistent.

[biskwikman]

thanks for the suggestions. I just wanted to check, the tests will have to be updated for this, right? It looks like two are failing now.

[Changaco]

The tests aren't failing with the latest commit. I think GitHub is still showing earlier test results because there's currently a merge conflict (because #2177 hasn't been deployed yet, because I've been waiting for new machine and human translations (liberapay/salon#520)).