Implement strategy to pass secrets during build time

[uniqueg]

Is your feature request related to a problem? Please describe.
Currently there is no way of conveniently passing secrets (FTP, database, broker credentials...) to the service during build time. As credentials cannot be version controlled, this presents a serious vulnerability.

Describe the solution you'd like
Research and implement possible solutions, possibly involving Kubernetes and/or Docker secrets.

Once in place, use strategy to pass secrets/credentials for:

• database (MongoDB)
• broker (RabbitMQ)
• object store (FTP)

Describe alternatives you've considered
N/A

Additional context
N/A

[uniqueg]

A strategy has been devised for Kubernetes/OpenShift deployment: default values are passed as in deployment/values.yaml during Helm installation. See separate instructions in Helm Kubernetes/OpenShift install documentation. The strategy has been implemented for both the database and the .netrc file required for accessing FTP storage. Implement analogously for broker. Compare with #63 and resolve together.