Extending the fulfilment modal

[kkerti]

Is your feature request related to a problem? Please describe.
Vendure's extensibility is it's main appeal to me. What the vendure team achieved in decoupling complex ecommerce patterns is awesome. But when a part of the core strikes back with a rigid, non-extensible section, development gets really discouraging.

The fulfilment modal, where an operator can pick which line items are being fulfilled lacks extensibility. In our case, we would like to add serial number input fields for each item.

Describe the solution you'd like
It would be great to have an UI extension target for the fulfilment modal. I think even custom fields could be set for fulfillments and those custom fields could be also presented as UI elements on the fulfilment modal. The UI for the different fulfilment handlers are put to a narrow sidebar, without proper visibility / emphasis for the UI. Rearrangement of the fulfilment handlers would come in handy as well.

For our own fulfilment solution, we would like to see a list input field (multiselect or similar), where we can enter serial numbers manually or with a barcode reader. For example if we were using a barcode reader and the fulfilment UI is active, we would create custom logic to increment the fulfilled line item quantity input field (part of the default fulfilment flow) and also enter the serials next to the line item where the custom logic suggests.

Describe alternatives you've considered
Following a similar logic to one of pinelab's stock management plugin, the fulfilment part of the order management would be outsourced to a third party solution. The third party solution would then sync back the necessary fulfilment info to vendure.

On a discord question @michaelbromley suggested a custom menubar action which opens a custom modal.

Additional context
As a hardware startup, right now we follow through all of our finished product's lifecycle. We manufacture them, create the serial numbers for them and then based on incoming orders, we fulfil them. All these steps take place in a single location right now. The stock location is where the vendure operators are working. In our case, vendure admin panel's further extensibility would mean higher coordination between manual product moving steps and it's administration in vendure.

This subject was briefly discussed on discord:
https://discord.com/channels/1100672177260478564/1300387792299491352