`@ParametersAreNonnullByDefault` and all parameters and return types are
    never null unless explicitly annotated `@Nullable`.

 *  **Warning: this release is source-incompatible for Kotlin users.**
    Nullability was previously ambiguous and lenient but now the compiler will
    enforce strict null checks.

 *  New: The response message is now non-null. This is the "Not Found" in the