Shopify app to integrate API for shipping labels

You are required to build a shopify app that will connect to an existing REST API (documentation will be provided) that will allow to generate and download shipping labels (PDF) for the existing orders.

The app must have the following functions:

1 Configuration. Will let the user:
    a) Manage API credentials (API key)
    b) Default insurance settings (on/off)
    c) Default shipping method (express/standard)
    d) Default package data (weight and measures)
    e) Default sender address (street, number, city, state, zip code)

2 Order list. Will let the user see a list of orders, sort them by column and filter them by status:

    a) Will let the user select one or multiple orders to generate the shipping labels (1.for each selected order the app will send to the REST API the shipping address of the order and the configured default package, sender address and other settings; 2.the server will store the requests and send a confirmation or error reply and will enqueue the label generation on backend; 3.when each label is generated on backend the API will call a webhook on Shopify end with the the link to the PDF or an error message)
   
    b) Will let the user download the shipping Label (PDF file) of each order or see the error message if that's the case (allowing the user to edit the shipping details and retry the process)

We expect to get fully documented source code and support to upload the app to the shopify marketplace.

Please send any questions as a private message.