API DNS is hard coded in nginx.config

[agentmilindu]

https://github.com/scorelab/Bassa/blob/b7668b90fc4e703a3313e21e62d6115b9fbd5e1c/ui/nginx.conf#L3

Helm is using release name as a prefix for the service names to enable the ability to deploy multiple instances of an application. However, as the service DNS is hardcoded in the nginx.conf in the Docker, this is not possible. This should be passable via ENVs.