Upgrade to swagger-request-validator / openapi-request-validator 3.0.0

[jpraet]

swagger-request-validator has been moved to github and renamed to openapi-request-validator

https://github.com/atlassian/openapi-request-validator

There is a new 3.0.0 release with some breaking changes.

The automatic dependency upgrade by dependabot broke some tests, so I have pinned it to 2.x for now.

[pvdbosch]

openapi-request-validator 3.0 requires Spring 7 / SBv4 , and also JDK21 which is a higher minimum requirement than SBv4.
I think we shouldn't raise minimum requirements for everyone only for this optional integration.

If we want to test that the new version causes no regressions, we could think of adding an "openapi-request-validator-3" Maven profile, that's only used to launch relevant tests with the replaced dependency.