docs: add status codes documentation (#549)

Signed-off-by: Gustavo Inacio <[email protected]>

docs/StatusCode.md

@@ -0,0 +1,26 @@
+# Status Codes
+
+The request handler may return various status codes depending 
+on the encountered errors. These codes provide insight into 
+what went wrong, without necessarily indicating how to fix the issue.
+
+## General Errors
+
+| **Status Code**             | **Name**                                            | **Description**                                                                                      |
+|-----------------------------|------------------------------------------------------|------------------------------------------------------------------------------------------------------|
+| `400 BAD_REQUEST`           | `TapCoreError(SignatureError or ReceiptError::CheckFailure)` | The received Tap-related data is invalid (e.g., incorrect signature or failed receipt check).      |
+| `402 PAYMENT_REQUIRED`      | `ReceiptNotFound`                                   | A required Tap receipt was not found in the request.                                                  |
+| `402 PAYMENT_REQUIRED`      | `EscrowAccount`                                     | The signer does not match any known sender or the domain for signature recovery is incorrect (as per the `[blockchain]` section in the config). |
+| `500 INTERNAL_SERVER_ERROR` | `TapCoreError(Other)`                               | An internal server error related to Tap core functionality, such as a failure in storing the receipt. |
+| `502 BAD_GATEWAY`           | `SerializationError`                                | The response from `graph-node` could not be serialized into a GraphQL response.                      |
+| `503 SERVICE_UNAVAILABLE`   | `QueryForwardingError`                              | The request could not be processed due to an error while forwarding the query to graph-node.     |
+
+## Status Query Errors
+
+These errors occur specifically during `status` operations:
+
+| **Status Code**     | **Name**                          | **Description**                                  |
+|---------------------|-----------------------------------|--------------------------------------------------|
+| `400 BAD_REQUEST`   | `InvalidStatusQuery`              | The query contains invalid status parameters.     |
+| `400 BAD_REQUEST`   | `UnsupportedStatusQueryFields`    | The query includes fields that are not supported. |
+| `502 BAD_GATEWAY`   | `StatusQueryError`                | An internal error was encountered during the status query process. |