Allow createConnection to contain tokens, so you can test OAuth connections

[taylorreece]

Most connections contain all of their data in .fields. OAuth connections have additional data in .token. This allows you to create a connection with .token populated. For example,

const sfConnection = createConnection(
  salesforceOAuth,
  {},
  {
    instance_url: "https://example.my.salesforce.com",
    access_token: "abc-123",
  }
);