Connect services to networks with the 'networks' key

Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>

tests/fixtures/networks/docker-compose.yml

@@ -1,7 +1,19 @@
 version: 2
 
-networks:
-  foo:
-    driver:
+services:
+  web:
+    image: busybox
+    command: top
+    networks: ["front"]
+  app:
+    image: busybox
+    command: top
+    networks: ["front", "back"]
+  db:
+    image: busybox
+    command: top
+    networks: ["back"]
 
-  bar: {}
+networks:
+  front: {}
+  back: {}

tests/fixtures/networks/missing-network.yml

@@ -0,0 +1,10 @@
+version: 2
+
+services:
+  web:
+    image: busybox
+    command: top
+    networks: ["foo"]
+
+networks:
+  bar: {}

tests/fixtures/no-services/docker-compose.yml

@@ -0,0 +1,5 @@
+version: 2
+
+networks:
+  foo: {}
+  bar: {}