Check for existence of auth tokens before publish (validate config stage?)

[noahnu]

Is your feature request related to a problem? Please describe.

Better to fail early if missing auth in non-dry run mode.

Describe the solution you'd like

Some sort of config validation at the beginning of the pipeline that fails fast.

[mcataford]

It would make sense to have something like ajv validate the configuration object before we proceed, yeah! Fun side-effect of this: the config schema would also serve as config format documentation. 🤔

[noahnu]

We do use ajv to validate the file config. The problem with auth is that it comes from yarn, and isn't passed in via CLI args or file options.