feat(ws): initial commit for backend

[ederign]

Scaffolding of the backend.

In this PR:

• basic Dockerfile
• basic Makefile
• Scaffold of App and first sample endpoint (http://localhost:4000/api/v1/healthcheck/)
• REST API basic infrastructure and error handling

[ederign]

@thesuperzapper @jiridanek I've updated my PR as we discussed.

I'll open a new issue to discuss the k8 client.

[google-oss-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jiridanek, thesuperzapper

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[thesuperzapper]

/lgtm