This removes 'spring.cloud.stream.sendto.destination' headers from each incoming message

Resolves #692

Add documentation

Resolves #676

Resolves #701
Resolves #702

Introduce auto-fallback to routing function if more then one function is present and no definition is provided.
Add explicit routing sample

Add documentation

Fixed consumer type

Fixed tests

Added javadoc @author tag

Resolves #699
Resolves #700

Add BeanResolver

Resolves #693

try upgrading sample version of adapter dependency

Restore GSON mapper preference

default to GSON if impl not specified

Resolves #690

Provide mutator/accessor for enhancer filed in FunctionInvocationWrapper
in SimpleFunctionRegistry. This is required by graalvm native compilation in
Spring Cloud Stream applications.

Resolves https://github.com/spring-cloud/spring-cloud-function/issues/689

Update documentation that GCF is GA, not Alpha

Resolves #680

Add test for collections

polishing

Resolves #685

Deprecate spring.http.converters.preferred-json-mapper
Resolves #677

 This commit also includes other minor fixes around CustomRuntime which was getting in the way of this specific issue
 Added lookup for _HANDLER env variable
 Added few tests (will need more)
 Added support for Iterable for reactive functions

Resolves #662

Prior to this it was based on existance of AWS_LAMBDA_RUNTIME_API env variable which turned out to be not very reliable since it is present in Java 11 runtime
With this commit it simple ensures that the handler is neither FunctionInvoker nor AbstractSpringFunctionAdapterInitializer

Resolves #673

Resolves #679

Resolves #678

Resolves #570