Hints for spring-cloud-dataflow-rest-client Spring Boot 3 port

[klopfdreh]

Problem description:
Currently we are trying to port our task applications to Spring Boot 3. Because we are using the spring-cloud-dataflow-rest-client in one of our task applications there are some binary incompatibilities as this package relies on Spring Boot dependencies. I already created a ticket to reduce dependencies: #5405.

To port the rest client I noticed two incompatibilities:

1. VndErrorResponseErrorHandler uses org.springframework.http.client.ClientHttpResponse.getStatusCode() which returns a HttpStatusCode instead of a HttpStatus
2. DataFlowClientAutoConfiguration uses OAuth2ClientPropertiesRegistrationAdapter with OAuth2ClientPropertiesRegistrationAdapter.getClientRegistrations(properties).values()) which can be replaced by OAuth2ClientPropertiesMapper with new OAuth2ClientPropertiesMapper(properties).asClientRegistrations().values()) see: https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.1-Release-Notes#deprecations-in-spring-boot-310

Solution description:
N/A

Description of alternatives:
N/A

Additional context:
N/A