Fix Checkov Security Scan Failures in Dockerfile

[chicks-net]

Problem

The Checkov security scanning workflow has been consistently failing across recent pull requests (#22, #23, #24, #25, #26) with the same Docker-related security issues.

Checkov Failures

The following security checks are currently failing:

1. CKV_DOCKER_7: "Ensure the base image uses a non latest version tag"

   • Issue: FROM coredns/coredns uses implicit latest tag
   • Fix: Use specific version like FROM coredns/coredns:1.11.1

2. CKV_DOCKER_2: "Ensure that HEALTHCHECK instructions have been added to container images"

   • Issue: No HEALTHCHECK instruction in Dockerfile
   • Fix: Add appropriate health check for CoreDNS

3. CKV_DOCKER_3: "Ensure that a user for the container has been created"

   • Issue: Container runs as root user
   • Fix: Create and switch to non-root user

Impact

• All recent PRs show failing Checkov scans
• Security best practices not being followed
• CI pipeline shows red status

Proposed Solution

Update the Dockerfile to address all three security issues:

• Pin CoreDNS to specific version
• Add health check using dig command
• Create and use non-root user for container execution

Files to Update

• Dockerfile
• Potentially update documentation if health check behavior changes

Priority

Medium - affects security posture and CI reliability but doesn't block functionality.