dry run migration

backend/tests/fixtures/migration_dry_run_fixture.json

@@ -0,0 +1,58 @@
+{
+  "source_dashboard_summary": [
+    {
+      "id": 42,
+      "title": "Sales"
+    }
+  ],
+  "target": {
+    "dashboards": [
+      {
+        "uuid": "dash-1",
+        "dashboard_title": "Sales Old",
+        "slug": "sales-old",
+        "position_json": "{}",
+        "json_metadata": "{}",
+        "description": "",
+        "owners": [
+          {
+            "username": "owner-a"
+          }
+        ]
+      }
+    ],
+    "datasets": [],
+    "charts": [],
+    "databases": []
+  },
+  "transformed_zip_objects": {
+    "dashboards": [
+      {
+        "uuid": "dash-1",
+        "title": "Sales New",
+        "signature": "{\"title\":\"Sales New\"}",
+        "owners": [
+          {
+            "username": "owner-b"
+          }
+        ]
+      }
+    ],
+    "charts": [
+      {
+        "uuid": "chart-1",
+        "title": "Chart A",
+        "signature": "{\"title\":\"Chart A\"}",
+        "dataset_uuid": "dataset-404"
+      }
+    ],
+    "datasets": [
+      {
+        "uuid": "dataset-1",
+        "title": "orders",
+        "signature": "{\"title\":\"orders\"}",
+        "database_uuid": "db-missing"
+      }
+    ]
+  }
+}