Refactor gates creating service, repository and tests

tests/resources/mock_gates.json

@@ -0,0 +1,24 @@
+{
+  "gateA": {
+    "name": "Gate A",
+    "id": "1"
+  },
+  "gateB": {
+    "name": "Gate B",
+    "id": "2",
+    "status": 0
+  },
+  "gateC": {
+    "name": "Gate C",
+    "id": "3"
+  },
+  "gateD": {
+    "name": "Gate D",
+    "id": "4",
+    "status": 0
+  },
+  "gateE": {
+    "name": "Gate E",
+    "id": "5"
+  }
+}