fix: #3018 - storing the pending changes

[monsieurtanuki]

New file:

• dao_transient_operation.dart: Transient operation: a minimalist product with a key.

Impacted files:

• barcode_product_query.dart: minor refactoring
• local_database.dart: added reference to new class DaoTransientOperation
• Podfile.lock: wtf
• product_refresher.dart: minor refactoring
• pubspec.lock: wtf

What

• Here, the main change is the new class DaoTransientOperation, where we will store "minimalist" products
  • when we add a background task, the first thing we will do is to store the minimalist product there
  • until the background task is completed, this is where we'll find the pending changes, to be used by the app, that will show the product as stored as the downloaded product, with those pending changes on top
  • when the background task is completed we download the latest version of the product - at this moment we can remove the corresponding minimalist products as they are integrated into the latest downloaded version

Part of

• Background + offline incoherences on multiple offline edits #3018

[M123-dev]

Thanks @monsieurtanuki no real functionality change here. Just one little naming comment but feel free to ignore that. 👍🏼

[M123-dev]

From the name I would guess that it would return all TransientOperation's not only the ones for a specific product, not that important as the barcode is not optional.

[monsieurtanuki]

Thank you @M123-dev for your review!
I understand your comment but on the other hand getAllForBarcode would be a bit verbose - and there's no plan for a getAll method without barcode either.
We'll see in the next steps, methods may be renamed later.