T987: Unclutter PPTP/IPSec RADIUS configuration nodes

In other words, remove top level tag nodes from radius-server and introduce
a regular "radius" node, thus we can add additional features, too. A migration
script is provided in vyos-1x which takes care of this config migration.

Change VyOS CLI from:

vyos@vyos# show vpn pptp
 remote-access {
     authentication {
         mode radius
         radius-server 172.16.100.10 {
             key barbarbar
         }
         radius-server 172.16.100.20 {
             key foofoofoo
         }
     }

To:

vyos@vyos# show vpn l2tp
 remote-access {
     authentication {
         mode radius
         radius {
             server 172.16.100.10 {
                 key barbarbar
             }
             server 172.16.100.20 {
                 key foofoofoo
             }
         }
     }

1 files changed, 59 insertions, 0 deletions

diff --git a/src/migration-scripts/pptp/0-to-1 b/src/migration-scripts/pptp/0-to-1
new file mode 100755
index 000000000..d0c7a83b5
--- /dev/null
+++ b/src/migration-scripts/pptp/0-to-1
@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+
+# Unclutter PPTP VPN configuiration - move radius-server top level tag
+# nodes to a regular node which now also configures the radius source address
+# used when querying a radius server
+
+import sys
+
+from vyos.configtree import ConfigTree
+
+if (len(sys.argv) < 1):
+    print("Must specify file name!")
+    sys.exit(1)
+
+file_name = sys.argv[1]
+
+with open(file_name, 'r') as f:
+    config_file = f.read()
+
+config = ConfigTree(config_file)
+
+cfg_base = ['vpn', 'pptp', 'remote-access', 'authentication']
+if not config.exists(cfg_base):
+    # Nothing to do
+    sys.exit(0)
+else:
+    # Migrate "vpn pptp authentication radius-source-address" to new
+    # "vpn pptp authentication radius source-address"
+    if config.exists(cfg_base + ['radius-source-address']):
+        address = config.return_value(cfg_base + ['radius-source-address'])
+        # delete old configuration node
+        config.delete(cfg_base + ['radius-source-address'])
+        # write new configuration node
+        config.set(cfg_base + ['radius', 'source-address'], value=address)
+
+    # Migrate "vpn pptp authentication radius-server" tag node to new
+    # "vpn pptp authentication radius server" tag node
+    for server in config.list_nodes(cfg_base + ['radius-server']):
+        base_server = cfg_base + ['radius-server', server]
+        key = config.return_value(base_server + ['key'])
+
+        # delete old configuration node
+        config.delete(base_server)
+        # write new configuration node
+        config.set(cfg_base + ['radius', 'server', server, 'key'], value=key)
+
+        # format as tag node
+        config.set_tag(cfg_base + ['radius', 'server'])
+
+    # delete top level tag node
+    if config.exists(cfg_base + ['radius-server']):
+        config.delete(cfg_base + ['radius-server'])
+
+    try:
+        with open(file_name, 'w') as f:
+            f.write(config.to_string())
+    except OSError as e:
+        print("Failed to save the modified config: {}".format(e))
+        sys.exit(1)