Docker build secrets support

[smebberson]

Adds Docker build secrets support: c d build can pass --secret id=...,env=... build arguments, configured via the project's c.js docker locations.

Related PRs

• 1Password secret references for local Kubernetes secret manifests #101 - 1Password secret references for manifest templates (independent; both touch bin/lib/c-kc.js, so whichever merges second needs a trivial rebase).

Notes

• Adds formatBuildSecrets to bin/lib/c-kc.js and wires it into bin/c-d-build.js.
• Secrets can be configured as an array or an object (with function values supported, consistent with build args); object keys become the secret id (lowercased, hyphens to underscores), and values prefixed with $ name the environment variable to read from.

Verification and testing

Verification

• Without this change, c d build has no way to pass --secret flags through to Docker builds.

Testing

• Configure secrets on a docker location in a project's c.js and run c d build <location>; confirm the --secret id=...,env=... flags appear in the Docker build invocation.

Deployment

• No post-deployment steps; released with the next version of @idearium/cli.