bundles/apt: use node.os and node.os_version to determine settings

bundles/apt/files/apt.conf-unattended-upgrades

@@ -1,6 +1,10 @@
 Unattended-Upgrade::Origins-Pattern {
-        "origin=Debian,codename=${node.metadata['os_release']},label=Debian";
-        "origin=Debian,codename=${node.metadata['os_release']},label=Debian-Security";
+        "origin=Debian,codename=${os_release},label=Debian";
+        "origin=Debian,codename=${os_release},label=Debian-Security";
+
+% if node_has_backports:
+        "a=${os_release}-backports,n=${os_release}-backports";
+% endif
 
         // External packages
 % for item in sorted(data.get('origins', set())):

bundles/apt/files/sources.list-buster

@@ -0,0 +1,3 @@
+deb http://deb.debian.org/debian/ buster main non-free contrib
+deb http://security.debian.org/debian-security buster/updates main contrib non-free
+deb http://deb.debian.org/debian/ buster-updates main contrib non-free

bundles/apt/items.py

@@ -1,3 +1,12 @@
+supported_os = {
+    'debian': {
+        10: 'buster',
+    },
+}
+
+assert supported_os[node.os][node.os_version[0]], '{}: OS {} {} is not supported by bundle:apt'.format(node.name, node.os, node.os_version)
+
+
 actions = {
     'apt_update': {
         'command': 'apt-get update',
@@ -13,7 +22,11 @@ files = {
     '/etc/apt/apt.conf.d/50unattended-upgrades': {
         'content_type': 'mako',
         'source': 'apt.conf-unattended-upgrades',
-        'context': {'data': node.metadata.get('apt', {}).get('unattended-upgrades', {})}
+        'context': {
+            'data': node.metadata.get('apt', {}).get('unattended-upgrades', {}),
+            'node_has_backports': ('backports' in node.metadata.get('apt', {}).get('repos', {})),
+            'os_release': supported_os[node.os][node.os_version[0]],
+        }
     },
     '/etc/apt/apt.conf.d/20auto-upgrades': {
         'source': 'apt.conf-auto-upgrades',
@@ -27,10 +40,15 @@ files = {
     '/var/lib/cloud': {
         'delete': True,
     },
+    '/etc/apt/sources.list': {
+        'source': 'sources.list-{}'.format(supported_os[node.os][node.os_version[0]]),
+    },
 }
 
 directories = {
-    '/etc/apt/sources.list.d': {},
+    '/etc/apt/sources.list.d': {
+        'purge': True,
+    },
 }
 
 pkg_apt = {