Fabio Custom Backend opts lists all metadata

[webmutation]

Hi, I implemented a simple Custom Backend in Go for Fabio due to the health check validity of K8S services not being discovered, it seemed like the simplest solution.

However when adding the metadata of the service as Opts field all options show up... I am not sure this is a bug or if its by design...
It seems it will accept any KV map as input...

I am also abusing a bit the proto property, by using the schema http:// instead of the protocol string http and then doing a parsing... but since it does not seem to be validating it works...