Adopt Docker secrets to store credentials

[giohappy]

Consider Docker secrets to keep secured credentials, moreover if a common VM is used for multiple deployments

[cezio]

Which credentials should be stored in this way?

• geoserver admin
• geonode admin (it's provided by fixture at the moment, it can be created from cli instead)

• db access (requires super to create database, but access can be used with limited account)

  did i miss anything?

[giohappy]

the ones you listed are enough from my point of view....