configureable api endpoint

### Is your proposal related to a problem?
Using docker image for hasura, I have the need for a REST endpoint, however our API gateway already registers `/api` and as such hasura is rest endpoints are unreachable

### Describe the solution you'd like
an environment variable that allows the `/api` part (or more) to be configurable, eg to use `/public-api` instread

### Describe alternatives you've considered
Reconfiguring our API gateway, however this would have too much of a hit on our client that use our other internal APIs

Start by locating the Docker image configuration, environment-variable handling, and REST endpoint routing used by Hasura. Confirm how the `/api` path is currently selected and define completion as allowing it to be changed to a path such as `/public-api` without breaking existing REST endpoints.

Written by the indexing model from the issue text.