Improve Dockerfile

[abrahamko]

Currently the main Dockerfile suffers from the following problems:

• [ ] No .dockerignore - Meaning ALL files and folders are part of the Dockerfile context (It can't be overestimated, this is a big disadvantage)
• [ ] Container base image may be scratch instead of alpine - needs investigation
• [ ] Tools from busybox should not be present in production - clear unnecessary tools and remove them after use
• [ ] Change secrets-provider to secrets-provider-for-k8s throughout the file
• [ ] Consider Srdjan comment 1, Srdjan comment 2