rpc: extend writePermissions and readPermissions with the invoice entity

In the prior commit, we added a new set of permissions and also a new
entity: “invoices”. We’ll add this set of entities to the read and
write permissions accordingly as well to ensure that the existing
macaroons have access to all the items that the invoice.macaroon does.

rpcserver.go

@@ -69,6 +69,10 @@ var (
 			Entity: "info",
 			Action: "read",
 		},
+		{
+			Entity: "invoices",
+			Action: "read",
+		},
 	}
 
 	// writePermissions is a slice of all entities that allow write
@@ -98,6 +102,12 @@ var (
 			Entity: "info",
 			Action: "write",
 		},
+		{
+			Entity: "invoices",
+			Action: "write",
+		},
+	}
+
 	// invoicePermissions is a slice of all the entities that allows a user
 	// to only access calls that are related to invoices, so: streaming
 	// RPC's, generating, and listening invoices.