redemption backend

[levalleux-ludo]

Changes:

• create a test backend to receive the redemption message
• manage redeemCallbackUrl and redeemCallbackHeaders parameters through the widget
• verify the wallet signature received in the message in the test backend (as an example - to verify it's easy to do it)
• adapt the script to allow direct javascript function to be called to show the redeem/finance widget
• fixed redemption widget: in case the deliveryInfo is sent to a backend, ensure privacy and user authentication #8
• fixes fix missing bosonStyle's font "Plus Jakarta Sans" #43 in the HTML example

How to test:

• start the test backend

  cd tests/redemptionBackend
  npm ci
  npm run dev
  

• run the widget app
• add the following url params: redeemCallbackUrl=http%3A%2F%2Flocalhost%3A3666
• redeem an exchange and check the delivery details have been sent to the test backend