feat: initial support for tapd methods

Author: jcbrand

README.md

@@ -42,6 +42,37 @@ Methods for working with the Lightning Network
 
 To connect to an LND node, authentication details are required.
 
+## Taproot Assets Support
+
+This library includes support for Taproot Assets via the `tapd` daemon. Currently supported methods:
+
+- **listTaprootAssetBalances**: List Taproot Asset balances
+
+## Tapd Authentication
+
+To connect to a Tapd node, authentication details are required, similar to LND.
+
+Export credentials via CLI or manually:
+
+Run `base64` on the tls.cert and admin.macaroon files to get the encoded
+authentication data to create the Tapd connection. You can find these files in
+the Tapd directory. (~/.tapd or ~/Library/Application Support/Tapd)
+
+    base64 -w0 ~/.tapd/tls.cert
+    base64 -w0 ~/.tapd/data/mainnet/admin.macaroon
+
+You can then use these to interact with your Tapd node directly:
+
+```node
+const {authenticatedTapdGrpc} = require('lightning');
+
+const {tapd} = authenticatedTapdGrpc({
+  cert: 'base64 encoded tls.cert file',
+  macaroon: 'base64 encoded admin.macaroon file',
+  socket: '127.0.0.1:10029',
+});
+```
+
 Export credentials via CLI:
 [balanceofsatoshis](https://github.com/alexbosworth/balanceofsatoshis):
 `npm install -g balanceofsatoshis` and export via `bos credentials --cleartext`
@@ -393,3 +424,7 @@ variables set:
     Verify that a chain address message has a valid ECDSA signature
 - [verifyMessage](https://github.com/alexbosworth/ln-service#verifymessage): Check that a
     message from a node in the graph has a valid signature.
+
+## Taproot Assets Methods
+
+- **listTaprootAssetBalances**: List Taproot Asset balances grouped by asset ID or group key.

grpc/protos/tapcommon.proto

@@ -0,0 +1,36 @@
+syntax = "proto3";
+
+package taprpc;
+
+option go_package = "github.com/lightninglabs/taproot-assets/taprpc";
+
+// Represents a Bitcoin transaction outpoint.
+message OutPoint {
+    /*
+    Raw bytes representing the transaction id.
+    */
+    bytes txid = 1;
+
+    /*
+    The index of the output on the transaction.
+    */
+    uint32 output_index = 2;
+}
+
+// A transaction outpoint annotated with TAP-level asset metadata. It uniquely
+// identifies an asset anchored at a specific outpoint.
+message AssetOutPoint {
+    // The outpoint of the asset anchor, represented as a string in the
+    // format "<txid>:<vout>". The <txid> is the transaction ID of the UTXO,
+    // hex-encoded and byte-reversed (i.e., the internal little-endian
+    // 32-byte value is reversed to big-endian hex format) to match standard
+    // Bitcoin RPC and UI conventions.
+    string anchor_out_point = 1;
+
+    // The asset ID of the asset anchored at the outpoint.
+    bytes asset_id = 2;
+
+    // The script key of the asset. This is the taproot output key that the
+    // asset is locked to.
+    bytes script_key = 3;
+}