refactor: improve code testability

[Alkaar]

There is no functional code change here. This was simply to refactor the code so I can leverage scalatest and mockito. Most of the work was to expose the Resy API so it can be mocked and the rest of the code can be tested. Minor refactors were made along the way.

• Breakout Resy API into a ResyApi class so it can be mocked
• Create ResyClient to take in ResyApi object as an argument (or in a testing use case, a mocked version of it)
• Moved workflow code outside of the main driver code for ease of readability since most people will be modifying the driver and the workflow code can be distracting
• Other minor improvements

[github-actions]

🚀 PR was released in v1.0.0 🚀