lnrpc: add arguments for stateless wallet initialization to wallet unlocker

This commit adds the --stateless_init flag to all three wallet unlocker
operations. Once you initialize a wallet stateless, you need to set
this flag for every further wallet unlocker operation. Otherwise you
risk non-encrypted macaroon information to leak to the underlying
system.

lnrpc/walletunlocker.proto

@@ -141,8 +141,24 @@ message InitWalletRequest {
     recover the funds in each channel from a remote force closed transaction.
     */
     ChanBackupSnapshot channel_backups = 5;
+
+    /*
+    stateless_init is an optional argument instructing the daemon NOT to create
+    any *.macaroon files in its filesystem. If this parameter is set, then the
+    admin macaroon returned in the response MUST be stored by the caller of the
+    RPC as otherwise all access to the daemon will be lost!
+    */
+    bool stateless_init = 6;
 }
 message InitWalletResponse {
+    /*
+    The binary serialized admin macaroon that can be used to access the daemon
+    after creating the wallet. If the stateless_init parameter was set to true,
+    this is the ONLY copy of the macaroon and MUST be stored safely by the
+    caller. Otherwise a copy of this macaroon is also persisted on disk by the
+    daemon, together with other macaroon files.
+    */
+    bytes admin_macaroon = 1;
 }
 
 message UnlockWalletRequest {
@@ -171,6 +187,12 @@ message UnlockWalletRequest {
     recover the funds in each channel from a remote force closed transaction.
     */
     ChanBackupSnapshot channel_backups = 3;
+
+    /*
+    stateless_init is an optional argument instructing the daemon NOT to create
+    any *.macaroon files in its file system.
+    */
+    bool stateless_init = 4;
 }
 message UnlockWalletResponse {
 }
@@ -187,6 +209,30 @@ message ChangePasswordRequest {
     daemon. When using REST, this field must be encoded as base64.
     */
     bytes new_password = 2;
+
+    /*
+    stateless_init is an optional argument instructing the daemon NOT to create
+    any *.macaroon files in its filesystem. If this parameter is set, then the
+    admin macaroon returned in the response MUST be stored by the caller of the
+    RPC as otherwise all access to the daemon will be lost!
+    */
+    bool stateless_init = 3;
+
+    /*
+    new_macaroon_root_key is an optional argument instructing the daemon to
+    rotate the macaroon root key when set to true. This will invalidate all
+    previously generated macaroons.
+    */
+    bool new_macaroon_root_key = 4;
 }
 message ChangePasswordResponse {
-}
+    /*
+    The binary serialized admin macaroon that can be used to access the daemon
+    after rotating the macaroon root key. If both the stateless_init and
+    new_macaroon_root_key parameter were set to true, this is the ONLY copy of
+    the macaroon that was created from the new root key and MUST be stored
+    safely by the caller. Otherwise a copy of this macaroon is also persisted on
+    disk by the daemon, together with other macaroon files.
+    */
+    bytes admin_macaroon = 1;
+}