CallFn execute function fn without validations, fn must have signature of func(context.Context, any) (any, error).

InitArgument init argument struct of fn, fn must have signature of func(context.Context, any) (any, error).

InitResult init result struct of fn, fn must have signature of func(context.Context, any) (any, error).

ValidateFn validation function, will only success if fn has signature of func(context.Context, any) (any, error).