Add integration tests for the releaser CLI

The following discussion from !6 (merged) should be addressed:

• @steveazz started a discussion: (+1 comment)

  What do you think if we add an integration test here? We start a mock server, pass in the address and call the command and assert that we get the correct data 🤔 ? We can also make the mock server return for example 401 and assert that we log something to the user thanks to logrus hook