Search improvement about bonsai

[impworks]

Seems to be working fine for actual data. Closing this for now.

[impworks]

Discussion in #104 revealed that the search, in fact, doesn't work fine. Some of the found issues are:

• Exact match can be outranked by other, seemingly unrelated matches
• Sometimes match fails/succeeds/fails during autocomplete as letters are added: e.g. for foobar in the database, fo - OK, foo - nothing found, foob - OK again, and so on.

Options to consider:

• Perform a thorough examination of the indices and search queries (unfortunately I have no idea how it works at all in the first place, its intricacies are way too convoluted and my experience is shallow, may be worth hiring someone)
• Upgrade Elasticsearch to 7.x, use built-in hunspell dictionaries instead of russian_morphology and see if it works better
• Replace Elasticsearch altogether with Postgresql search: https://habr.com/ru/post/438622/#comment_19743164 (which is especially cool since elasticsearch + java are huge dependencies, dropping them without compromising search quality would be awesome)

[DiverOfDark]

I am keen to investigate other solutions, i.e. Lucene.NET, but for that I need some test data, ideally unit-tests with samples that should work. You already have seed data, so it probably should not be that hard to implement 'em.

[impworks]

Great, will do that next week.