This makes all requests async. Synchronous requests simply block on their thread.
(cherry picked from commit 62903c4)
(cherry picked from commit 2f4caa6)
(cherry picked from commit 3b1df8b) Conflicts: pom.xml retrofit-converters/jackson/pom.xml retrofit-converters/pom.xml retrofit-converters/protobuf/pom.xml retrofit-converters/simplexml/pom.xml retrofit-converters/wire/pom.xml retrofit-mock/pom.xml retrofit/pom.xml samples/github-client/pom.xml samples/mock-github-client/pom.xml samples/pom.xml
There's a bit of a test gap going on for all the variants of successful and erroneous handling of sync, async, and rx. This new behavior is fully tested in all three but more general behavior testing for them will be needed in in a follow-up.
…ctly. This allows service APIs to use Callback subtypes and mock behavior together. Previously this would have thrown an exception due to the internal assumption that all asynchronous APIs were declared using Callback directly.
…ler but alows us to provide the Executor.