Add CentOS 8.0 OS

Author: t-tran

upcloud_api/constants.py

@@ -27,6 +27,7 @@ class OperatingSystems(object):
     templates = {
         'CentOS 6.10': '01000000-0000-4000-8000-000050010200',
         'CentOS 7.6': '01000000-0000-4000-8000-000050010300',
+        'CentOS 8.0': '01000000-0000-4000-8000-000050010400',
         'Debian 8.11': '01000000-0000-4000-8000-000020030100',
         'Debian 9.9': '01000000-0000-4000-8000-000020040100',
         'Debian 10.0': '01000000-0000-4000-8000-000020050100',