Add unit tests for InvoicingPeriodDraftOverlay and reference suggestion logic, including fake DB integration and aggregation methods

- Implemented `InvoicingPeriodDraftOverlayTest` with coverage for blocking and permitting invoicing actions based on draft states, transactions, and metadata.
- Created `ReferenceSuggestionsApiTest` to validate ranked and filtered suggestions across bookings, orders, and vehicles with varied match relevance, context, and frequency.
- Added `order_reference_suggestions_service` class, including query methods, normalization utilities, and aggregation logic for reference suggestions.
- Enhanced query handling in `InvoicingPeriodDraftOverlayFakeDb` to validate SQL constraints and column cache resets in overlapping invoicing contexts.

services/nginx/app/tests/Support/Api/ApiFixtures.php

@@ -935,13 +935,44 @@ final class ApiFixtures
         return $attributeId;
     }
 
+    public function preserveModuleConfig(string $module, string $variable): void
+    {
+        $existing = $this->fetchModuleConfig($module, $variable);
+        $conditions = [
+            'module' => $module,
+            'variable' => $variable,
+        ];
+
+        $this->cleanup->add(function () use ($conditions, $existing): void {
+            if ($existing === null) {
+                $this->deleteWhereIfPossible('module_config', $conditions);
+                return;
+            }
+
+            $current = $this->fetchModuleConfig((string)$conditions['module'], (string)$conditions['variable']);
+            $data = [
+                'value' => $existing['value'] ?? null,
+                'type' => $existing['type'] ?? null,
+                'created_at' => $existing['created_at'] ?? null,
+                'updated_at' => $existing['updated_at'] ?? null,
+            ];
+
+            if ($current === null) {
+                $this->insertRow('module_config', [
+                    'module' => $existing['module'] ?? $conditions['module'],
+                    'variable' => $existing['variable'] ?? $conditions['variable'],
+                    ...$data,
+                ]);
+                return;
+            }
+
+            $this->updateWhere('module_config', $conditions, $data);
+        });
+    }
+
     public function setModuleConfig(string $module, string $variable, string $value, string $type = 'bool'): void
     {
-        $moduleEscaped = $this->db->real_escape_string($module);
-        $variableEscaped = $this->db->real_escape_string($variable);
-        $existing = $this->queryOneBySql(
-            "SELECT * FROM module_config WHERE module = '{$moduleEscaped}' AND variable = '{$variableEscaped}' LIMIT 1"
-        );
+        $existing = $this->fetchModuleConfig($module, $variable);
 
         if ($existing !== null) {
             $conditions = [
@@ -1876,6 +1907,16 @@ final class ApiFixtures
         return $row ?: null;
     }
 
+    private function fetchModuleConfig(string $module, string $variable): ?array
+    {
+        $moduleEscaped = $this->db->real_escape_string($module);
+        $variableEscaped = $this->db->real_escape_string($variable);
+
+        return $this->queryOneBySql(
+            "SELECT * FROM module_config WHERE module = '{$moduleEscaped}' AND variable = '{$variableEscaped}' LIMIT 1"
+        );
+    }
+
     private function setRedisJson(string $key, array $payload): void
     {
         if ($this->redis === null) {