Add support for no-argument Supplier and single-argument Consumer function callbacks in the Spring AI core module. This enhancement allows: - Registration of Supplier callbacks with no input (Void) type - Registration of Consumer callbacks with no output (Void) type - Support for Kotlin Function0 (equivalent to Java Supplier) - Handle empty properties for Void input types in schema generation - Enhance FunctionCallback builder to support Supplier/Consumer patterns

Additional changes: - Add test coverage for both Supplier and Consumer callbacks in various scenarios - Enhance TypeResolverHelper to support Consumer input type resolution - Support lambda-style function declarations for improved ergonomics - Add test cases for void input/output handling in OpenAI chat model - Include examples of function calls without return values - Add support for parameterless functions through Supplier interface

Resolves #1718 , #1277 , #1118, #860

Comment From: markpollack

Refactored some of the long methods so that it reads more cleanly. Added 'final' to the kotlin delegate classes.

Comment From: markpollack

in the docs, the section "Customization Options" was empty, so I removed it.

Comment From: markpollack

merged in 432954dad7f7c3a33117848a4259bc7076865c5f