Purpose
=======
When an operator is doing a vendor purchase receipt, they may receive
items from different orders without having a direct clear view on which
ones they are.
They should be able to do their receipt in the Barcode app without
wondering about that and just get a suggested batch if items belong to
different orders.

Functionnality
==============
When an operator scans a product which isn't reserved in the currently
opened operation, a prop will be displayed to ask the user if they want
to batch the receipt with another receipt which contains the scanned
product.
The user can either batch with another receipt, either add the product
or either discard (do nothing, don't add the scanned product.)
If they chose to batch with another receipt, both receipts (the current
one and the selected one) will be batched together, either in a new
batch (if none were already in a batch), either in one of the pickings'
batch.
If both receipts are already in a different batch, their both batches
should be merged together (whihch can result in more than one added
picking.)

The same thing happens if the user tries to add a product with the
`stock.move.line` form view (with the "Add Product" button), the same
confirmation dialog will be displayed, and if the user choses to batch,
the created move's `picking_id` will be set on the selected picking, and
the batch will be opened instead of going back picking.

Once the pickings are batched, one of the batched move lines for the
scanned product will be incremented and after that, when the batch is
opened in the Barcode app, this move line will be auto-selected.
So, for the user, the product they scanned before batching the receipt
isn't lost, they don't need to re-scan it.
Note that this implementation is very basic, it doesn't handle scan of
lot/serial numbers nor packages for now.

Also note that this feature doesn't require to enable the batch setting,
it should work even if this setting is disabled.

How suggest receipts to batch are chosen
========================================
For a receipt to appear in the suggest batch pop-up, it should match
following requirement
- It must share with the opened receipt the same contact, the same
  company and the same state (to avoid to batch confirmed pickings with
  draft pickings);
- It can't be done nor cancelled.

[task-6154300](https://www.odoo.com/odoo/966/tasks/6154300)

Sometimes people want to share some specific slots one after the other without having to tediously set them one by one.

## Add a "clone last slot" / "clone last day" action in the list view

This eases the set up when most days look the same. The copying is done based on the timezone of the appointment so that the result is always consistent.

## Rework the slot editor

### Custom appointments

Previously you could create an appointment via the calendar view, which would allow you to select some slots visually in the calendar before sharing them.

We rework this system to be able to edit existing appointments, move and delete slots.
This removes the appointment dropdown at the top of the calendar and replaces it with a sidebar where you can create and manage appointments where you are an organizer, which would previously have been listed in the dropdown.

From there you can copy the url to share it, enter edition mode to make sure the correct slots are bookable, or edit some basic settings of the appointment type.

In this settings form, a new duration field is available that will automatically create slots every X minutes as the user drags. Which is a common thing users want to do for example for house showings.
To prevent users from accidentally creating way too many slots at once, this is limited to 24 hours at a time which should be more than sufficient.

### Recurring appointments

It is also possible to edit recurring appointments by going to their form using a new stat button.
It works very similarly to the custom appointments except slots are only split around midnight.

Bookable slots (those shown in the frontend, called "subslots" in this code) are represented inside each slot.
Depending on duration and "create slots every X hours" settings of the appointment type.

##  Old slots garbage collection

To avoid cluttering the slots for long-lived appointments, a new garbage collection mechanism is added to remove slots older ending over 1 week ago, always leaving the last 40 slots so users can have an idea of what the schedule was like on old unused appointment types.


task-5072614