Investigate use of Spring Cloud Contracts

[jamietanna]

Spring Cloud Contracts is a great project for performing Consumer Driven Contract development.

As well as being a Spring Cloud project - therefore being a little easier to integrate with Spring Boot - we can also use it as a Docker image, allowing us to not require running it on just Java/Spring Boot project.

The project also has support for being able to quite nicely integrate with Pact, which is pretty widely used i.e. in GDS.

We should investigate setting up the project to execute against contracts, potentially against a separate repository that we can use to manage all contracts and stubs

See also:

• https://cloud.spring.io/spring-cloud-contract/reference/html/gradle-project.html
• Gradle projects don't run out-of-the-box with JUnit5 mode spring-cloud/spring-cloud-contract#1744