Fix: Related Content should be fetched during the fetch pipeline

[1yam]

In case of store message, the related content (file) isn't fetched during the fetch pipeline but is direcly fetched while processing it, making the processing block for no reason.

Related Clickup or Jira tickets : ALEPH-XXX

Self proofreading checklist

• Is my code clear enough and well documented
• Are my files well typed
• Are there enough tests

Changes

This pull request refactors the message verification and content fetching flow to ensure that database sessions are consistently passed and that related content is fetched at the appropriate stage. It also updates tests to reflect these changes and ensures required files are present in the database before processing messages. The changes improve reliability and maintainability by enforcing a clearer separation of concerns between message verification, balance checking, and content fetching.

Core handler refactor:

• The verify_message method in MessageHandler now requires a session argument and performs a balance pre-check within the method, streamlining the verification and pre-check process. (src/aleph/handlers/message_handler.py)
• The process method no longer performs a separate balance pre-check or fetches related content; these responsibilities have been moved to the verification stage, simplifying the processing pipeline. (src/aleph/handlers/message_handler.py)

Content fetching pipeline update:

• The pending message fetch job now explicitly fetches related content (such as IPFS files) after message verification, ensuring all dependencies are loaded before further processing. (src/aleph/jobs/fetch_pending_messages.py)

Test suite updates:

• Multiple tests now insert required files into the database before processing messages and fetch related content after verification, ensuring test reliability and alignment with the new handler logic. (tests/message_processing/test_process_forgets.py, tests/message_processing/test_process_stores.py, tests/test_network.py) [1] [2] [3] [4] [5] [6] [7] [8] [9]

Imports and setup:

• Added missing imports for file upsert and file type in test modules to support new test setup requirements. (tests/message_processing/test_process_forgets.py, tests/message_processing/test_process_stores.py) [1] [2] [3]

Notes

There is still an issue with the pinning of message blocking the pipeline, but better to be block during the fetch than the processing

[odesenfans]

1. Remove the changes inherited by #871, they're out of focus
2. Check permissions in the fetch pipeline
3. To discuss: IMO we should keep on pinning files in the processing pipeline as well, I see the fetch pipeline as a way to speed things up but the processing pipeline should have the full logic to be 100% sure that files get stored properly.

[odesenfans]

Looking pretty good, just one more comment.