Expose Vulnerabilities::StateTransition ID in GraphQL

What does this MR do and why?

Expose Vulnerabilities::StateTransition ID in GraphQL

How to set up and validate locally

query {
  vulnerability(id: "gid://gitlab/Vulnerability/<ID>") {
    id
    stateTransitions {
      nodes {
        id
        fromState
        toState
      }
    }
  }
}