Add indication of how to configure application on 3rd party provider

[laissandrade]

We need to document which callback url he must add. For example:

auth.myproject.wedeploy.io/oauth/token

Or, for local development:

auth.myproject.wedeploy.me/oauth/token

[laissandrade]

Also add information on how to configure environment variables via dashboard:

[zenorocha]

Yes, we have a plan for that, one page per service type explaining all the env variables and then link to them.