[API] Add authentication
There's currently an API_KEY environment variable that has no use as of yet. This should be implemented so that everyone can use their own instance of the API. Of course, you can choose to make it public if you want, but this should just be the default when setting up your own instance.
I initially did not add it because the actual API and bot working was the main focus, but now that that is somewhat done, I can move on to improvements.
This should make use of tsoa's way with authentication as shown here, however I feel like it should be a Authorization: THE_API_KEY type of thing, just basically using headers.