behaviour of find_trees with ottTaxonName

[kcranston]

What should happen in these two cases:

• there are multiple ottIDs that match the taxon name (could return additional field with other matching name / ids, or a boolean multiple_matches field)
• there is no ID that matches the taxon name

[josephwb]

For ottId a bad id returns:

{"matched_studies": []}

So a bad name should do the same. Or update both to be more explicit.

[kcranston]

Simply returning an empty list doesn't differentiate between "there are no trees for this taxon" and "this taxon does not exist". If that distinction is useful, then we should probably return a 400 for the latter case.

Still open question about what to do in cases where the name matches multiple IDs. Is that an error, too?