Add environment variables to set up a cluster without manual steps

I'm trying to run couchbase/server:community-4.5.0 in a Kubernetes StatefulSet. It would be tremendously helpful if this docker image exposed a number of environment variables to configure the nodes automatically.

• MASTER_NODE
• PORT
• RAM_SIZE_MB
• INDEX_RAM_SIZE_MB
• FTS_RAM_SIZE_MB
• SERVICES
• STORAGE_SETTING
• USER
• PASSWORD

On the first node to be created this action could initialize the cluster:

couchbase-cli cluster-init \
  --cluster-username=${USER} \
  --cluster-password=${PASSWORD} \
  --cluster-port=${PORT} \
  --services=${SERVICES} \
  --cluster-ramsize=${RAM_SIZE_MB} \
  --cluster-index-ramsize=${INDEX_RAM_SIZE_MB} \
  --cluster-fts-ramsize=${FTS_RAM_SIZE_MB} \
  --index-storage-setting=${STORAGE_SETTING}

On the other nodes they would run the following command to get added to the cluster:

couchbase-cli rebalance \
  --cluster=${MASTER_NODE}:${PORT} \
  --user=${USER} \
  --password=${PASSWORD} \
  --server-add=$(hostname):${PORT} \
  --server-add-username=${USER} \
  --server-add-password=${PASSWORD} \
  --service=${SERVICES}

Start by inspecting the repository's Dockerfiles and configuration scripts for the couchbase/server:community-4.5.0 image, then compare startup behavior with the proposed cluster-init and rebalance commands. Determine how the listed variables should control first-node initialization and additional-node joining in a Kubernetes StatefulSet. Done means the image can create and expand the cluster without manual steps.