Add deployed_version endpoint

[atolopko-czi]

Motivation

The deployed version is not easily determined. It requires digging through AWS ECS TaskDef setting.

Definition of Done

An deployed_version should be added that reports the git commit SHA1 of the deployed Docker image build.

Tasks

• GHA and/or Docker build updates to set the commit sha1 at build time (see Portal repo)
• Add endpoint
• Update On-Call Deployment checklist to have eng check the endpoint after deploy (same as for Portal)

[atolopko-czi]

This is (at least) the third time we've added this issue! I'll keep this one, and close the others, since it follows the latest issue template.

• [FEATURE REQUEST] Add /deployed_version endpoint to Explorer #106
• Update version based on commit hash #51