Restrict laji.fi observation search to logged in users

[esko-piirainen]

As laji.fi / PAP / API user I'd like our services to be responsive

Bots are crawling especially https://laji.fi/observation/finnish section heavily, causing load on Warehouse/Vertica.

[mikkohei13]

First require login just on the tilastointi (aka beta) section.

[mikkohei13]

@Blodir See for example https://laji.fi/vihko/templates, which is already limited to registered users only.