Investigate using S-C-Contract Stub Runner instead of Hoverfly for contract testing

[ojhughes]

We had previously discounted Wiremock because of issues where a set of interactions span multiple requests. Using S-C-Contracts, it should be possible to run multiple stub servers, one for each CF service eg api.cf.., login.cf...` etc.

Using S-C-Contracts should be preferred as it is a Spring project! (So Hoverfly is maybe a stop gap solution)

see https://github.com/spring-cloud/spring-cloud-contract/tree/master/spring-cloud-contract-stub-runner