split GRAFANA_URL again into GRAFANA_URL and GRAFANA_PROXY_URL

GRAFANA_URL is the docker internal URL that worker-grafana-dashboard and worker-grafana-user-orgs need to access the GrafanaAPI. While GRAFANA_URL=http://proxy./visualization/ works locally, it does not work on the VMs, due to an SSL Error. When the GRAFANA_URL=${PROXY_URL}/visualization/ is used it works on the VMs but doesn't work locally (as the worker containers would try to access the api on their localhost respectively).

By accessing the visualization container directly with GRAFANA_URL=http://visualization:3000 the Grafana API can be accessed both locally and on stage/prod.

GRAFANA_PROXY_URL=${PROXY_URL}/visualization/ is used for the visualization container as it is needed to provide the correct redirect-url when using Oauth.

merged

assigned to @joost.hemmen1

mentioned in commit 674791d4