fallback on Main rubygems.org API of dependency API is down

[mkristian]

recently rubygem.org had problems with the dependency API for a day or two. during this time the gem-artifacts basically failed since the generated pom.xml and maven-metadata.xml depends on the info deliverd by that dependency API.

it is possible to use the info the from the MAIN rubygems.org api which is more download and slower and more memory consumption.

[mkristian]

it should propagate the dependency API in a way that the client falls back to the main rubygems.org API. doing a fallback on the server is not feasible.