Implement Github Actions Continuous Delivery pipeline

[jujaga]

Description

This PR implements the rest of the remaining CI/CD pipeline, preserving as much of the original deployment semantics and formatting as possible.

• Implement Github Actions Continuous Delivery pipeline
• Drop Jenkins, add Security Policy and update Readme

SHOWCASE-3447

Types of changes

New feature (non-breaking change which adds functionality)
Documentation (non-breaking change with enhancements to documentation)
Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• I have read the CONTRIBUTING doc
• I have checked that unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the OpenAPI 3.0 v*.api-spec.yaml documentation (if appropriate)
• I have added necessary documentation (if appropriate)

Further comments

[github-actions]

Coverage Report

Totals
Statements:	97.02% ( 750 / 773 )
Methods:	98.04% ( 100 / 102 )
Lines:	98.57% ( 415 / 421 )
Branches:	94% ( 235 / 250 )