Feature: Send attachments to widget user (#621)

app/javascript/dashboard/api/inbox/message.js

@@ -19,6 +19,17 @@ class MessageApi extends ApiClient {
       params: { before },
     });
   }
+
+  sendAttachment([conversationId, { file, file_type }]) {
+    const formData = new FormData();
+    formData.append('attachment[file]', file);
+    formData.append('attachment[file_type]', file_type);
+    return axios({
+      method: 'post',
+      url: `${this.url}/${conversationId}/messages`,
+      data: formData,
+    });
+  }
 }
 
 export default new MessageApi();