Draft: Resolve "Refactoring the infrastructure"

Closes #26

Update workflow:

• using only a single staging branch with multiple dev merge requests
• the main deployment happens based on versioned tags (support rollback when needed)
• protect main and staging branches
• plan how to test notebooks individually (binderhub)
• plan how to update major packages (hackathons)
• plan how to run notebooks anonymously (and safely)
• make sure that "short-urls" still works
• make sure that sensitive notebooks have not been shared publicly (Please note that analytics is a public repository)

Update Dockerfile:

• Multi-stage build (builder, base, final)
• predetermine common package requirements
• cron job to rebuild image regularly
• fine-tune header generation (using as a preprocess instead of running it at build time)
• revisit example data storage (right now it is 3.1G) (#18)

Update CI/CD pipeline:

• update jupyterhub's chart
• To get rid of ananlytics-deployment dependencies.
  • Store all sensitive data in env variables
  • Move all deployment configurations here
• having cleanup processes (images, environments)
• using ingress controller