contract-tests: Add contract tests for consuming fabric8-auth service.

[pmacik]

This PR adds the consumer side of the contract tests for the Tenant service consuming Auth service API endpoints.

PR CICO job: openshiftio/openshiftio-cico-jobs#997

The provider side (Auth service) of the contract tests is covered by fabric8-services/fabric8-auth#711

Story: https://jira.coreos.com/browse/ODC-249
Task: https://jira.coreos.com/browse/ODC-476

[codecov]

Codecov Report

Merging #767 into master will increase coverage by 0.54%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #767      +/-   ##
==========================================
+ Coverage   75.01%   75.56%   +0.54%     
==========================================
  Files          38       38              
  Lines        3146     3278     +132     
==========================================
+ Hits         2360     2477     +117     
- Misses        585      600      +15     
  Partials      201      201

Impacted Files	Coverage Δ
configuration/configuration.go	70.61% <0%> (-0.48%)	⬇️
update/versions.go	100% <0%> (ø)	⬆️
openshift/types.go	93.75% <0%> (+1.25%)	⬆️
environment/service.go	97.81% <0%> (+6.14%)	⬆️
environment/type.go	60% <0%> (+6.15%)	⬆️

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[MatousJobanek]

Sorry for my late review.
This looks good, thanks a lot for doing these tests 👍