I do not agree to use
host all all 0.0.0.0/0 md5
if your database is exposed to the internet. In my project postrgres is in the cloud and it is used from the backend. I need to connect directly to the database only for maintenance. I connect to the database from a public IP, say 126.96.36.199. In this case the correct entry is:
host mybackend myuser 188.8.131.52/0 ...