See: Refused to set unsafe header "Content-length"

Not perfect, but at least makes it readable.
Things to correct at some point in time: very obscure return_gateways_array and move route delete actions to configd

Taken from: https://translate.opnsense.org/

Also inline the tab function while there.

(legacy) quite obscure, return_gateways_array, but it's probably better to return an ip if we know the gateway...