docs: add Paystack Adapter usage example

docs/assets/examples/paystack.md

@@ -0,0 +1,108 @@
+# 💳 Paystack Adapter Usage Example
+
+This guide demonstrates how to use the **`PaystackAdapter`** in **EasySwitch** to initialize, verify, and manage payments through [Paystack](https://paystack.com).
+
+---
+
+## ⚙️ Setup
+
+Make sure you have **EasySwitch** installed:
+
+```python
+# Using pip
+pip install easyswitch
+
+# Or using uv
+uv add easyswitch
+```
+
+Then export your Paystack secret key as an environment variable:
+```python
+export EASYSWITCH_PAYSTACK_SECRET_KEY=sk_test_yourkeyhere
+```
+
+## 🧠 Configuration Example
+
+Using `EasySwitch.from_dict()` **(unified-multi-provider usage)**
+```python
+from easyswitch import EasySwitch, Provider
+
+client = EasySwitch.from_dict({
+    "providers": {
+        Provider.PAYSTACK: {
+            "api_key": "sk_test_yourkeyhere",
+            "environment": "sandbox",
+            "callback_url": "https://example.com/callback",
+            "return_url": "https://example.com/return",
+            "timeout": 30
+        }
+    }
+})
+```
+
+## 💡 Example: Initialize a Payment
+Using the EasySwitch client
+```python
+# Assuming client = EasySwitch.from_dict(...) as shown earlier
+from easyswitch.types import TransactionDetail, CustomerInfo, Currency, Provider
+
+tx = TransactionDetail(
+    transaction_id="tx_example_001",
+    amount=500.0,  # 500.00 NGN (adapter converts to kobo)
+    currency=Currency.NGN,
+    customer=CustomerInfo(email="[email protected]", phone_number="+2348012345678"),
+    reference="ref_example_001", # unique per payment
+    provider=Provider.PAYSTACK
+)
+
+res = await client.send_payment(tx)   
+print("Link:", res.payment_link)
+```
+
+## 🔍 Check status / get transaction detail / refunds
+
+```python
+# check status (by reference)
+status_resp = await client.check_status("ref_example_001")
+print("Status:", status_resp.status)   # TransactionStatus enum
+print("Amount:", status_resp.amount)
+
+# get full transaction details (by transaction id)
+tx_detail = await client.get_transaction_detail("123456789")  
+print(tx_detail.status, tx_detail.amount, tx_detail.customer.email)
+
+# refund (pass transaction id and optional amount in main units)
+refund_resp = await client.refund(transaction_id="123456789", amount=100.0)
+print("Refund status:", refund_resp.status, "amount:", refund_resp.amount)
+```
+
+## ⚠️ Notes
+- Test Mode:
+ Use your sk_test_... key for sandbox testing. You’ll get URLs like:
+```python
+ https://checkout.paystack.com/abcd1234
+```
+
+- Live Mode:
+ When you switch to a live key (sk_live_...), your URLs will look like:
+```python
+ https://paystack.com/pay/your-page-id
+```
+
+- Reference Uniqueness:
+Each transaction must have a unique reference string.
+
+- Timeouts:
+The timeout in your config controls how long the adapter waits for a Paystack response.
+
+
+## 🧰 Troubleshooting
+| Error | Cause | Fix |
+| :--- | :--- | :--- |
+| `PaymentError: 400` | Invalid reference or payload | Ensure **API keys** are correct and **callback URL** is valid. (Often caused by missing or improperly formatted required data). |
+| `TimeoutError` | Paystack unresponsive or network delay | Increase `config.timeout` (e.g., from 30 to 60 seconds). |
+
+
+## 🔗 Related Documentation
+- [Paystack API Reference](https://paystack.com/docs/api/)
+- [EasySwitch Core Reference](https://alldotpy.github.io/EasySwitch/)

easyswitch/integrators/paystack.py

@@ -129,7 +129,7 @@ async def send_payment(self, transaction: TransactionDetail) -> PaymentResponse:
         async with self.get_client() as client:
             response = await client.post(
                 "/transaction/initialize",
-                json=payload,
+                json_data=payload,
                 headers=self.get_headers()
             )
 
@@ -194,7 +194,7 @@ async def refund(self, transaction_id: str, amount: Optional[float] = None) -> P
             if amount:
                 payload["amount"] = int(amount * 100)  
 
-            response = await client.post("/refund", json=payload, headers=self.get_headers())
+            response = await client.post("/refund", json_data=payload, headers=self.get_headers())
 
             data = response.json() if hasattr(response, "json") else response.data
             if response.status in range(200, 300) and data.get("status"):