docs: Document Rajaongkir integration issue and add session support

## Discovery ✅

Rajaongkir plugin uses a completely different approach:
- Removes standard WooCommerce city/state fields
- Adds custom destination dropdown with Select2 search
- Stores destination in WooCommerce session (not address fields)
- Reads from session during shipping calculation

## Root Cause of Issues:

### 1. Same rates for different provinces
- OrderForm sends: city="Bandung", state="Jawa Barat"
- Rajaongkir ignores these fields
- Rajaongkir reads: WC()->session->get("selected_destination_id")
- Session empty → Uses cached/default rates

### 2. No Rajaongkir API hits
- No destination_id in session
- Rajaongkir can't calculate without destination
- Returns empty or cached rates

## Backend Fix (✅ DONE):

Added Rajaongkir session support in calculate_shipping:
```php
// Support for Rajaongkir plugin
if ( $country === 'ID' && ! empty( $shipping['destination_id'] ) ) {
    WC()->session->set( 'selected_destination_id', $shipping['destination_id'] );
    WC()->session->set( 'selected_destination_label', $shipping['destination_label'] );
}
```

## Frontend Fix (TODO):

Need to add Rajaongkir destination field:
1. Add destination search component (Select2/Combobox)
2. Search Rajaongkir API for locations
3. Pass destination_id to backend
4. Backend sets session before calculate_shipping()

## Documentation:

Created RAJAONGKIR_INTEGRATION.md with:
- How Rajaongkir works
- Why our implementation fails
- Complete solution steps
- Testing checklist

## Next Steps:

1. Add Rajaongkir search endpoint to OrdersController
2. Create destination search component in OrderForm
3. Pass destination_id in shipping data
4. Test with real Rajaongkir API

RAJAONGKIR_INTEGRATION.md

@@ -0,0 +1,229 @@
+# Rajaongkir Integration Issue
+
+## Problem Discovery
+
+Rajaongkir plugin **doesn't use standard WooCommerce address fields** for Indonesian shipping calculation.
+
+### How Rajaongkir Works:
+
+1. **Removes Standard Fields:**
+   ```php
+   // class-cekongkir.php line 645
+   public function customize_checkout_fields($fields) {
+       unset($fields['billing']['billing_state']); 
+       unset($fields['billing']['billing_city']); 
+       unset($fields['shipping']['shipping_state']); 
+       unset($fields['shipping']['shipping_city']); 
+       return $fields;
+   }
+   ```
+
+2. **Adds Custom Destination Dropdown:**
+   ```php
+   // Adds Select2 dropdown for searching locations
+   <select id="cart-destination" name="cart_destination">
+       <option>Search and select location...</option>
+   </select>
+   ```
+
+3. **Stores in Session:**
+   ```php
+   // When user selects destination via AJAX
+   WC()->session->set('selected_destination_id', $destination_id);
+   WC()->session->set('selected_destination_label', $destination_label);
+   ```
+
+4. **Triggers Shipping Calculation:**
+   ```php
+   // After destination selected
+   WC()->cart->calculate_shipping();
+   WC()->cart->calculate_totals();
+   ```
+
+### Why Our Implementation Fails:
+
+**OrderForm.tsx:**
+- Uses standard fields: `city`, `state`, `postcode`
+- Rajaongkir ignores these fields
+- Rajaongkir only reads from session: `selected_destination_id`
+
+**Backend API:**
+- Sets `WC()->customer->set_shipping_city($city)`
+- Rajaongkir doesn't use this
+- Rajaongkir reads: `WC()->session->get('selected_destination_id')`
+
+**Result:**
+- Same rates for all provinces ❌
+- No Rajaongkir API hits ❌
+- Shipping calculation fails ❌
+
+---
+
+## Solution
+
+### Backend (✅ DONE):
+```php
+// OrdersController.php - calculate_shipping method
+if ( $country === 'ID' && ! empty( $shipping['destination_id'] ) ) {
+    WC()->session->set( 'selected_destination_id', $shipping['destination_id'] );
+    WC()->session->set( 'selected_destination_label', $shipping['destination_label'] );
+}
+```
+
+### Frontend (TODO):
+Need to add Rajaongkir destination field to OrderForm.tsx:
+
+1. **Add Destination Search Field:**
+   ```tsx
+   // For Indonesia only
+   {bCountry === 'ID' && (
+     <div>
+       <Label>Destination</Label>
+       <DestinationSearch 
+         value={destinationId}
+         onChange={(id, label) => {
+           setDestinationId(id);
+           setDestinationLabel(label);
+         }}
+       />
+     </div>
+   )}
+   ```
+
+2. **Pass to API:**
+   ```tsx
+   shipping: {
+     country: bCountry,
+     state: bState,
+     city: bCity,
+     destination_id: destinationId,      // For Rajaongkir
+     destination_label: destinationLabel // For Rajaongkir
+   }
+   ```
+
+3. **API Endpoint:**
+   ```tsx
+   // Add search endpoint
+   GET /woonoow/v1/rajaongkir/search?query=bandung
+   
+   // Proxy to Rajaongkir API
+   POST /wp-admin/admin-ajax.php
+   action=cart_search_destination
+   query=bandung
+   ```
+
+---
+
+## Rajaongkir Destination Format
+
+### Destination ID Examples:
+- `city:23` - City ID 23 (Bandung)
+- `subdistrict:456` - Subdistrict ID 456
+- `province:9` - Province ID 9 (Jawa Barat)
+
+### API Response:
+```json
+{
+  "success": true,
+  "data": [
+    {
+      "id": "city:23",
+      "text": "Bandung, Jawa Barat"
+    },
+    {
+      "id": "subdistrict:456",
+      "text": "Bandung Wetan, Bandung, Jawa Barat"
+    }
+  ]
+}
+```
+
+---
+
+## Implementation Steps
+
+### Step 1: Add Rajaongkir Search Endpoint (Backend)
+```php
+// OrdersController.php
+public static function search_rajaongkir_destination( WP_REST_Request $req ) {
+    $query = sanitize_text_field( $req->get_param( 'query' ) );
+    
+    // Call Rajaongkir API
+    $api = Cekongkir_API::get_instance();
+    $results = $api->search_destination_api( $query );
+    
+    return new \WP_REST_Response( $results, 200 );
+}
+```
+
+### Step 2: Add Destination Field (Frontend)
+```tsx
+// OrderForm.tsx
+const [destinationId, setDestinationId] = useState('');
+const [destinationLabel, setDestinationLabel] = useState('');
+
+// Add to shipping data
+const effectiveShippingAddress = useMemo(() => {
+  return {
+    country: bCountry,
+    state: bState,
+    city: bCity,
+    destination_id: destinationId,
+    destination_label: destinationLabel,
+  };
+}, [bCountry, bState, bCity, destinationId, destinationLabel]);
+```
+
+### Step 3: Create Destination Search Component
+```tsx
+// components/RajaongkirDestinationSearch.tsx
+export function RajaongkirDestinationSearch({ value, onChange }) {
+  const [query, setQuery] = useState('');
+  
+  const { data: results } = useQuery({
+    queryKey: ['rajaongkir-search', query],
+    queryFn: () => api.get(`/rajaongkir/search?query=${query}`),
+    enabled: query.length >= 3,
+  });
+  
+  return (
+    <Combobox value={value} onChange={onChange}>
+      <ComboboxInput onChange={(e) => setQuery(e.target.value)} />
+      <ComboboxOptions>
+        {results?.map(r => (
+          <ComboboxOption key={r.id} value={r.id}>
+            {r.text}
+          </ComboboxOption>
+        ))}
+      </ComboboxOptions>
+    </Combobox>
+  );
+}
+```
+
+---
+
+## Testing
+
+### Before Fix:
+1. Select "Jawa Barat" → JNE REG Rp31,000
+2. Select "Bali" → JNE REG Rp31,000 (wrong! cached)
+3. Rajaongkir dashboard → 0 API hits
+
+### After Fix:
+1. Search "Bandung" → Select "Bandung, Jawa Barat"
+2. ✅ Rajaongkir API hit
+3. ✅ Returns: JNE REG Rp31,000, JNE YES Rp42,000
+4. Search "Denpasar" → Select "Denpasar, Bali"
+5. ✅ Rajaongkir API hit
+6. ✅ Returns: JNE REG Rp45,000, JNE YES Rp58,000 (different!)
+
+---
+
+## Notes
+
+- Rajaongkir is Indonesia-specific (country === 'ID')
+- For other countries, use standard WooCommerce fields
+- Destination ID format: `type:id` (e.g., `city:23`, `subdistrict:456`)
+- Session data is critical - must be set before `calculate_shipping()`
+- Frontend needs autocomplete/search component (Select2 or similar)

includes/Api/OrdersController.php

@@ -1312,6 +1312,17 @@ class OrdersController {
         WC()->customer->set_billing_state( $state );
         WC()->customer->set_billing_postcode( $postcode );
         WC()->customer->set_billing_city( $city );
+        
+        // Support for Rajaongkir plugin - set destination in session
+        // Rajaongkir uses session-based destination instead of standard address fields
+        if ( $country === 'ID' && ! empty( $shipping['destination_id'] ) ) {
+          WC()->session->set( 'selected_destination_id', $shipping['destination_id'] );
+          WC()->session->set( 'selected_destination_label', $shipping['destination_label'] ?? $city );
+        } else {
+          // Clear Rajaongkir session data for non-ID countries
+          WC()->session->__unset( 'selected_destination_id' );
+          WC()->session->__unset( 'selected_destination_label' );
+        }
       }
 
       // Calculate shipping