QUARKUS-1415 Reactive REST Client improvements

JIRA link: https://issues.redhat.com/browse/QUARKUS-1415

Test plan covers Reactive REST Client functionality provided by quarkus-rest-client-reactive extension.

Documentation: https://quarkus.io/version/main/guides/resteasy-reactive https://quarkus.io/version/main/guides/rest-client-reactive

Related test plans

QUARKUS-1075

Scope of the testing

Upload and download of large (more than 2Gb) files, see quarkusio/quarkus#22229 for details
Support for proxy authentication
New configuration schema introduced in quarkusio/quarkus#17220
Recursive sub-resources (see quarkusio/quarkus#22417)
Support for ParamConverter (related issue: quarkusio/quarkus#23486)
Manual check of Dev UI

Impact on test suites and testing automation:

Four new scenarios in QE TS
Upload and download of large (more than 2GB) files will add several minutes to the execution time
Additional impact for Native mode is expected to be around 4 minutes per new scenario
Overall time execution increase is ~20 minutes

Automated test development

Identify existing coverage in Quarkus integration tests.
Update existing RESTEasy Reactive scenarios

Advanced topics for test development

Automated tests for Dev UI