Refactor dashboard data serialization and mock context for improved clarity

- Introduced `serialize_audit_for_response` and `serialize_current_cluster_for_template` functions to handle JSON serialization of audit and cluster data, enhancing data consistency for API responses and template rendering.
- Updated `get_mock_context` in `mock_data.py` to utilize the new serialization functions, simplifying the mock data structure and improving readability.
- Refactored `collect_context` and `collect_audits` in `views.py` to leverage the new serialization methods, ensuring a cleaner and more maintainable codebase.
- Added unit tests for the new serialization functions to ensure correctness and reliability of data formatting.

dashboard/tests/test_serializers.py

@@ -0,0 +1,57 @@
+"""Tests for dashboard.serializers."""
+
+import json
+
+from django.test import TestCase
+
+from dashboard.serializers import (
+    serialize_audit_for_response,
+    serialize_current_cluster_for_template,
+)
+
+
+class SerializeAuditForResponseTest(TestCase):
+    def test_serializes_list_fields_to_json_strings(self):
+        audit = {
+            "id": "audit-1",
+            "name": "Test",
+            "migrations": [{"instanceName": "i1", "source": "h1", "destination": "h2"}],
+            "host_labels": ["h1", "h2"],
+            "cpu_current": [10.0, 20.0],
+            "cpu_projected": [15.0, 25.0],
+        }
+        result = serialize_audit_for_response(audit)
+        self.assertEqual(result["id"], "audit-1")
+        self.assertEqual(result["name"], "Test")
+        self.assertEqual(json.loads(result["migrations"]), audit["migrations"])
+        self.assertEqual(json.loads(result["host_labels"]), audit["host_labels"])
+        self.assertEqual(json.loads(result["cpu_current"]), audit["cpu_current"])
+        self.assertEqual(json.loads(result["cpu_projected"]), audit["cpu_projected"])
+
+    def test_leaves_already_serialized_strings_unchanged(self):
+        audit = {
+            "id": "a",
+            "migrations": "[1,2]",
+            "host_labels": "[]",
+            "cpu_current": "[0]",
+            "cpu_projected": "[0]",
+        }
+        result = serialize_audit_for_response(audit)
+        self.assertEqual(result["migrations"], "[1,2]")
+        self.assertEqual(result["host_labels"], "[]")
+        self.assertEqual(result["cpu_current"], "[0]")
+        self.assertEqual(result["cpu_projected"], "[0]")
+
+
+class SerializeCurrentClusterForTemplateTest(TestCase):
+    def test_serializes_lists_to_json_strings(self):
+        cluster = {"host_labels": ["c0", "c1"], "cpu_current": [30.0, 40.0]}
+        result = serialize_current_cluster_for_template(cluster)
+        self.assertEqual(json.loads(result["host_labels"]), cluster["host_labels"])
+        self.assertEqual(json.loads(result["cpu_current"]), cluster["cpu_current"])
+
+    def test_leaves_already_serialized_strings_unchanged(self):
+        cluster = {"host_labels": "[]", "cpu_current": "[]"}
+        result = serialize_current_cluster_for_template(cluster)
+        self.assertEqual(result["host_labels"], "[]")
+        self.assertEqual(result["cpu_current"], "[]")