Naming collision with "configuration" in the Ruby client

[RKushnir]

In the Ruby client there's 2 separate things that end up being named GraphHopperClient::Configuration:
https://github.com/graphhopper/directions-api-clients/blob/d69250ddf3c9280d0c61b6d85591650956455830/ruby/lib/directions-api-client/configuration.rb
and
https://github.com/graphhopper/directions-api-clients/blob/d69250ddf3c9280d0c61b6d85591650956455830/ruby/lib/directions-api-client/models/configuration.rb

As Ruby allows to re-open existing classes, there's no clear error message indicating this. These 2 things just get mixed together in an unexpected manner, making the gem unusable and failing with a confusing error.

[karussell]

Uhm, this is ugly. This might be related or identical to the following issue of swagger codegen: swagger-api/swagger-codegen#8283

We are thinking about switching to the successor of swagger in this PR, but this is not yet properly planned.