Adding very simple payment flow to NIP96

96.md

@@ -121,7 +121,7 @@ The `server` MUST link the user's `pubkey` string as the owner of the file so to
 - `413 Payload Too Large`: File size exceeds limit
 - `400 Bad Request`: Form data is invalid or not supported.
 - `403 Forbidden`: User is not allowed to upload or the uploaded file hash didnt match the hash included in the `Authorization` header `payload` tag.
-- `402 Payment Required`: Payment is required by the server, **this flow is undefined**.
+- `402 Payment Required`: Payment is required by the server, see [Payment required](#payment-required) section.
 
 The upload response is a json object as follows:
 
@@ -133,6 +133,8 @@ The upload response is a json object as follows:
   message: "Upload successful.",
   // Optional. See "Delayed Processing" section
   processing_url: "...",
+  // Optional. Required if payment is required
+  payment_request: "lnbc1...", 
   // This uses the NIP-94 event format but DO NOT need
   // to fill some fields like "id", "pubkey", "created_at" and "sig"
   //
@@ -315,6 +317,12 @@ Example Response:
 - `page` page number (`offset=page*count`)
 - `count` number of items per page
 
+## Payment required
+
+`servers` may require payment for file storage. In that case, the server SHOULD serve the normal response with a **402 Payment Required** status code and a the `payment_request` field filled with a LN invoice.
+
+Until the payment is done, the server SHOULD display a QR code in the url tag of the NIP-94 event response. When the payment is done, the server MUST swap the QR code for the uploaded file.
+
 ## Selecting a Server
 
 Note: HTTP File Storage Server developers may skip this section. This is meant for client developers.