This is not a final official fix but I'd like to create this PR to raise a bug that needs a bigger solution.

The implemented fix submitted is what we're using as a temporary fix until you guys figure this out :)

Here's the simplified version of the issue:

We want to support PATCH for vmboxes.
We created our custom cb_grid_vmboxes module that supports PATCH
For cb_grid_vmboxes.allow_methods we want to return the verbs we support
Without flattering the list, we don't get PATCH as supported (some other weird list of allow_methods verbs seems to be used -- we haven't looked into it)

Main reason solution needs help:
With flattening the list, crossbar_bindings will still attemp to call PATCH for cb_vmboxes which is undefined.  This generates an error in the logs, but since it's done in another process - yay for crossbar_bindings - this doesn't "break" anything.
Removed changes from api_resource and instead made the recommended change to api_util:allow_methods/4.
This seems to work well and makes sense.
Added support for PATCH to cb_vmboxes crossbar API endpoint.
Merge pull request #671 from aberke/crossbar-allow_methods-fix

Crossbar allow methods fix
Merge pull request #672 from aberke/cb_vmboxes-PATCH-support

Added support for PATCH to cb_vmboxes crossbar API endpoint.
KAZOO-3178: output object from view
KAZOO-3178: move fold anon fun to named fun
KAZOO-3178: cleanup spelling error, syntax, and non-existant module
KAZOO-3178: replace version binaries with macros
KAZOO-3178: update docs to show new summary result format
KAZOO-3178: start a cache for crossbar
KAZOO-3178: cache master account notification summary
KAZOO-3178: check the api version and set page_size
KAZOO-3178: extract the account id properly
KAZOO-3178: allow GET on notification
KAZOO-3178: merge account notifications in favor of system
KAZOO-3178: find json object with Value at Key from list of json objects
KAZOO-3178: remove useless test
KAZOO-3178: document accept override on query string
KAZOO-3178: check for accept override in request before rendering
response

route to alternative to_* function if appropriate