Use explicit network aliases, add appservice registration script

servers/mautrix/discord/config.yaml

@@ -27,7 +27,7 @@ homeserver:
 # Changing these values requires regeneration of the registration.
 appservice:
     # The address that the homeserver can use to connect to this appservice.
-    address: http://mautrix-discord:29334
+    address: http://as-mautrix-discord:29334
     
     # The hostname and port where this appservice should listen.
     hostname: 0.0.0.0

servers/mautrix/discord/registration.yaml

@@ -1,5 +1,5 @@
 id: mautrix-discord
-url: http://mautrix-discord:29334
+url: http://as-mautrix-discord:29334
 as_token: mR1qkqQ8XCgJ61ZkhPdPUfgrjpZFVUhwRqizD8AiAsPFKdHVtvwnNVAH4vvDKyks
 hs_token: F3WF7uirTPUwMoUNBObcjZghoOUikYkFZtV8yPI3l4UxrNvVOjndmW3ev7Ypl099
 sender_localpart: KFwAMWXBNgYvWToZxHzoxdUvFCGe7W4d