NIP-83 Wallet connect/bridge

Useful for clients wanting to intergrate non-custodal wallet features.

> Intended for use with bitcoin, but could be used with any invoice payment system that can pay invoices/create invoices/check payment status.

83.md

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+NIP-83
+======
+
+Wallet connect/bridge
+--------------
+
+`draft` `optional` `author:arcbtc`
+
+Useful for clients wanting to intergrate non-custodal wallet features.
+
+> Intended for use with bitcoin, but could be used with any invoice payment system that can pay invoices/create invoices/check payment status.
+
+## Motivation
+
+We wanted LNbits to have a funding source that pay invoices/create invoices/check payment status, all over nostr DMs. Simple plugins/middleware coud be made for lightning nodes that connect to the funding source.
+
+## Examples
+
+There are two simple clients sending json over [NIP04](https://github.com/nostr-protocol/nips/blob/master/04.md).
+
+1. `funding source client`: Attached to the funding source, the other built into another service/client.
+
+2. `service client`: Built into a service.
+
+### Creating an invoice
+
+`service client` sends `create_invoice` event:
+
+```json
+{ "create_invoice": {
+        "amount": int,
+        "memo": "<Optional[str]>",
+        "description_hash": "<Optional[bytes]>"
+}
+}
+```
+
+`funding source client` checks the pubkey has permission and sends `generated_invoice` event:
+
+```json
+{ "generated_invoice": {
+    "payment_hash": "<string>", 
+    "payment_request": "<string>"
+  }
+}
+```
+
+### Paying an invoice
+
+`service client` sends `pay_invoice` event:
+
+```json
+{ "pay_invoice": {
+        "invoice":  "<string>",
+        "note": "<Optional[str]>"
+}
+}
+```
+
+### Checking a payment in/out
+
+`service client` sends `check_payment` event:
+
+```json
+{ "check_payment": {
+    "payment_hash": "<string>"
+  }
+}
+
+```
+
+`funding source client` checks the pubkey has permission, checks the payment status and sends `payment_status` event:
+
+```json
+{ "payment_status": {
+    "paid": "<bool>"
+  }
+}
+```