feat: add cancel command

lnbits/extensions/watchonly/static/components/serial-signer/serial-signer.html

@@ -230,7 +230,12 @@
             </q-btn>
           </div>
           <div class="col-3">
-            <q-btn v-close-popup flat color="grey" class="float-right"
+            <q-btn
+              @click="cancelOperation"
+              v-close-popup
+              flat
+              color="grey"
+              class="float-right"
               >Cancel</q-btn
             >
           </div>

lnbits/extensions/watchonly/static/components/serial-signer/serial-signer.js

@@ -239,6 +239,18 @@ async function serialSigner(path) {
         }
         await this.writer.write(COMMAND_CONFIRM_NEXT + '\n')
       },
+      cancelOperation: async function () {
+        try {
+          await this.writer.write(COMMAND_CANCEL + '\n')
+        } catch (error) {
+          this.$q.notify({
+            type: 'warning',
+            message: 'Failed to send cancel!',
+            caption: `${error}`,
+            timeout: 10000
+          })
+        }
+      },
       hwwLogin: async function () {
         try {
           await this.writer.write(

lnbits/extensions/watchonly/static/js/utils.js

@@ -8,6 +8,7 @@ const COMMAND_WIPE = '/wipe'
 const COMMAND_SEED = '/seed'
 const COMMAND_RESTORE = '/restore'
 const COMMAND_CONFIRM_NEXT = '/confirm-next'
+const COMMAND_CANCEL = '/cancel'
 
 const DEFAULT_RECEIVE_GAP_LIMIT = 20