Error logging can break JSON responses from the REST API if display_errors is enabled

[MichelleBlanchette]

Some routes have multiple endpoints (support multiple HTTP methods) which causes all of the registered endpoints' permission_callback to be ran as WordPress determines which HTTP methods are available for each registered REST API route.

This implies two things for us:

1. We shouldn't use log methods that display errors (but WordPress VIP hosting doesn't allow file writes outside of /wp-content/uploads)
2. We shouldn't use advanced permission checks, such as Asana_Interface::has_connected_asana()

Relates to https://github.com/PurpleTurtleCreative/completionist/issues/134