feat: test vp exchange with ew role vc

[nichonien]

This PR tests VP exchange for an Energy Web role VC using vc-api.

[nichonien]

@jrhender @JGiter @artursudnik Is there any way we can mock the CacheClient module such that we have access to intermediate results (credential argument of addStatusToCredential method) ? js.mock() only takes path of the module and iam-client-lib only has Dist build but not the src directory.

[JGiter]

I would try something like

const addStatusToCredential = jest.fn();
jest.mock('iam-client-lib', () => {
   return jest.fn().mockImplementation(() => {
    return {CacheClient: {addStatusToCredential}};
  });
})

[nichonien]

I tried this, it breaks other functions coming from iam-client-lib . So my assumption is that it mocks whole iam-client-lib not just the function as jest.mock() is for modules. - https://jestjs.io/docs/mock-functions#mocking-modules