[Peterborough] Disable pin snapping for new tree requests

We don't want to plant trees where there are already trees, so we add a
separate layer for new tree requests, and disable pin snapping for that
layer.

This adds a new option for layers named "relevant". If provided it will
be called with an options object, allowing you to check ".category" and
".group" and return a boolean for whether you want to display the layer
based on the passed options.

Note: You still need to provide an "asset_group" option even if you use
the "relevant" option as this is used elsewhere.

The "regular" tree-points layer uses this to exclude just the new trees
subcategory from being displayed.

0 files changed, 0 insertions, 0 deletions