Adds support for defining a default Docker registry. e.g. if `config.registryUrls = [‘https://docker.company.com']` then lookups for packages like `node` will be done from docker.company.com instead of index.docker.io.
As mentioned in #2315 some docker registries don't support the digest header. This PR falls back to parsing the resulting manifest if the header is present.
Closes#2315
Adds support for processing www-authenticate Header to obtain a token from the Docker servers. In particular, this enables Artifactory to work (without username/passwords for now). This is backwards-compatible to Docker Hub which issues this header with the current hard-coded URLs.
Removes custom Docker lookup code and instead integrates it with the generic lookup routine used by other package managers. Logic for digest support was added but is used by Docker-only for now.
Closes#2081, Closes#2276
Adds support for custom docker registries. To work (for now), registries must support anonymous public access to their v2 API. Tested against quay.io and gcr.io, including tags pagination for quay. Also needed to add a 10s timeout for registry queries to catch private/firewalled registries that we can't access.
Closes#797
