Expanding on your code for scheduling appointments

[datatalking]

I enjoyed your video on the doctors booking software page so I downloaded your code and found there are a few issues. Would like to help you build these features if we can.

1. There is no requirements.txt file so I created one of those, will you accept a PR?
2. The 'decouple' import doesn't exist but the 'python-decouple' does exist but I can bypass that if I run python3 manage.py runserver. Was your code intended for only a specific version of python?
3. How can we setup a model that the doctors office updates so a user cannot book time already taken?
4. How can we setup a way to reschedule if the doctors office gets a note that the doctor is sick, each user based on FIFO would reselect dates and times they want.