Small tweaks with exceptions.

Document that JAXB doesn't work on Android

Add a test for not overwriting headers.

To break the test, use Headers.Builder.set instead of add in ServiceMethod.

Fix local converter name.

Don't ever pass fatal errors to the callback.

Replace 'compile' with 'implementation

* Add missing nullability annotations.

* Inline single-use utility methods.

* Remove redundant throws.

* Inline method only called once.

Use HTTPS links in documentation where possible.

Closes: https://github.com/square/retrofit/issues/2425

Update to OkHttp 3.10.0.

Assert full JSON document consumption with Moshi.

Assert full JSON document consumption with Gson.

Update Scala dependency

This avoids a vulnerability on older 2.7 versions.

Since Call instances can be canceled externally, re-using that state for disposed means that some results were not delivered.

Rename the Scala adapter package to retrofit2.adapter.scala.

Previously it was retrofit2.converter.scala.