[Tagging] beer_garden

[Dave F]

It appears many of us (UK only?) have been misinterpreting the meaning 
of biergarten to represent outdoor seating areas of pubs.

To rectify I'm changing the value to 'beer_garden' for the ones in my 
area when specific areas are mapped as a polygon, but there seems a lack 
of agreement on the key:

https://taginfo.openstreetmap.org/search?q=beer_garden#values

Even though there's only five, I prefer 'leisure' as it ties in with 
'leisure=garden' (389000)
Amenity seems incorrect as the garden is a sub-feature of amenity=pub. 
Similarly for 'landuse'

Suggestions?

DaveF