taxon: fallback to fuzzy search for taxa via /v1/search?sources=taxa

[synrg]

When a user searches for a taxon and "Nothing found" is returned, it clutters the channel and requires additional work by the user (either by making additional attempts in channel or going to the web) to find the taxon they expected to match. We can help improve the user experience here with better error messages offering guidance as to why their query may have failed, but more importantly, try to avoid the failure in the first place through use of iNat's own "fuzzy match" search through their /v1/search?sources=taxa API. Here are some notes I jotted down earlier on #bot-stuff on the iNat Discord server:

• improve meaningfulness of error messages when the request would give you no results
  • offer tip about correct syntax when it's a syntax problem, as in only one item specified with ,related
  • offer help when nothing was matched about improving your chances of matching
• but otherwise, try to avoid giving no results
  • first use /v1/taxa/autocomplete
  • as a fallback, use /v1/search?q=xxx&sources=taxa and if the query was complex (i.e. has filters) then apply those filters on the results afterwards
  • only report Nothing found if both tries fail

[synrg]

I thought this would help, but the big deal killer is taxa must have the first 5 letters typed accurately or else fuzzy matching does not apply. This means it is only mildly useful and perhaps more annoying with all its false hits than in its ability to accurately return the one thing you were interested in at the top of its list. It hardly seems worth it.