Small doc improvements:
- Add the 2 missing parameters postgresql.existingSecret and postgresql.existingSecretKey in the list.
- Update the "Using an external PostgreSQL server" part by specifying how to use an existing postgresql Secret
***NO_CI***
The ingress.hostname entry listed in the README is erroneous and not used in the ingress.yaml file.
This change corrects the documentation to correctly refer to ingress.hosts and list the default value as given in values.yaml.
***NO_CI***
* fix wiki helm
* update readme
* include service account as a stub
* use lightweight healthz for readiness and health endpoint
* remove if block for setting DB_TYPE, only postgres is supported in this chart for now
