Is your feature request related to a problem? Please describe.

I'd like to use Ory Oathkeeper with:

• Traefik Forward Auth: (example)
  • Implementation is required
  • Document set up (with example config) in Oathkeeper -> Scenarios (new section!) ->Nginx ForwardAuth
• Nginx Subrequest:
  • Implementation should already work with the existing decisions endpoint
  • Document set up (with example config) in Oathkeeper -> Scenarios (new section!) ->Nginx ForwardAuth
• Ambassador Ambassador AuthService Plugin:
  • Implementation should already work with the existing decisions endpoint
  • Document set up (with example config) in Oathkeeper -> Scenarios (new section!) ->Ambassador AuthService Plugin
• Envoy External Authorization
  • Research is needed to decide if a custom endpoint is required or not
  • Document set up (with example config) in Oathkeeper -> Scenarios (new section!) -> Envoy External Authorization

Additional info

As per my comment #265 (comment) we would like to offer one endpoint per service:

• /decisions/generic/... (this is currently /decisions)
• /decisions/traefik/...
• ...

For backwards compatibility ideas see https://github.com/ory/oathkeeper/pull/265/files#r329310302

For implementation ideas see this PR: #265

Context

See comment #263 (comment)