feat: delay step transition until all media is processed

[jozsefdamokos]

fixes: #10822

• moved away from processing media in parallel messages
• all media processing is done in MediaProcessingProcessor now

[MalteJanz]

@jozsefdamokos thanks for the PR description 👍 . Some thoughts on these points from my side 😅

• moved away from processing media in parallel messages

Alright, no shame in doing so and it makes things a lot simpler for us to reason about which is better then race condition bugs on customer systems 👍

• changed MediaFileProcessorService to only dispatch a single ProcessMediaMessage instead of multiple messages. Only once this message is handled a new MigrationProcessMessage is dispatched. Then the processor calls the MediaFileProcessorService which then dispatches the next ProcessMediaMessage and so on.
• moved updating the progress of the media entities from MediaProcessingProcessor to ProcessMediaHandler

Taking a step back, does that make sense to you? To me it sounds like we don't need ProcessMediaMessage and ProcessMediaHandler at all anymore and just merge the necessary logic or refactoring it into MediaProcessingProcessor (which is called during the handling of MigrationProcessMessage) or the service that it is calling MediaFileProcessorService (which then shouldn't dispatch messages anymore). That way we don't jump between different message types and our code is much easier to reason about I think 🤔

• changed each ProcessMediaMessage to hold 20 media files to process instead of the previous 5.

Also sounds reasonable to me. Did you somehow manage to measure how long the processing of these messages take with that "batch size", ideally downloading from a remote server like a Shopware build (ShopDev) instance? We should just make sure we stay well below the 30s request timeout limit (in case someone migrates with the admin worker instead of proper cli worker).

[jozsefdamokos]

@MalteJanz Yes, I thought about merging them, I just chose the quicker way for now to validate that this approach works. I agree, we should merge the two now if the approach of moving away from parallel processing is fine.

[MalteJanz]

LGTM 👍 , only found one more file that can be removed now I think 🙂