is it possible to define policies through a configuration file?

Yes. Check out policies.json

so how would i go about supplying my own? when i issue a

find . -name 'policies.json'

from the root of my datahub-gms container to figure out where I would need to mount it, the only hit is

/tmp/jetty-0_0_0_0-8080-war_war-_-any-7932461418719180655/webapp/WEB-INF/classes/boot/policies.json