Improvements to Sorties de Stocks

[jniles]

This issue details suggestions/improvements/bugs found while reviewing #5341.

Bug: Submit button can be active while form is invalid

The submit button can be active when the form isn't valid. This is a corner case that happens when the date is changed. I think this is due to asynchronous validation that waits to block the submit button until the HTTP request is finished returning from the server. It's pretty easy to reproduce though:

This bug exists on master, so it does not block #5341. It is a critical bug though and should be addressed as soon as possible.

Proposal: if only one lot exists for an inventory item, auto-select it

On the stock exit, when we have a single lot for an inventory item, let's select it by default. There is a slight risk that users will start to be lazy and no longer check that the lot is the correct lot. However, I think the benefit to power users outweighs the risk of laziness.

I've discussed this proposal with @lomamech in person and he agrees with it as well.

Feature Request: Implement caching of the exit grid

In invoices, we have the ability to cache the grid when we submit, and restore it via a button. From a user perspective, it would be useful to do this for the stock exit. We would need to move a lot of our validation checks from the client to the server though, to prevent errors happening from stale data.

Motivation: for the Health Zone project, users often get to the very end of an exit document, realize they need to change the date and that erases all their work - sometimes hours of work. This is worth implementing to avoid this scenario, despite the development complexity.

[jniles]

I'm going to tackle the "invalid submit button" states part of this issue.