Multiple notifications when receiving single message with media attachment(s)

• I have searched open and closed issues for duplicates
• I am submitting a bug report for existing functionality that does not work as intended
• I have read https://github.com/signalapp/Signal-Android/wiki/Submitting-useful-bug-reports
• This isn't a feature request or a discussion topic

Bug description

When a contact sends a message with multiple images attached, I receive multiple notifications for the same message -- one for each image -- instead of a single notification for the entire message.

Steps to reproduce

1. Have a contact send you a message with multiple images
2. Watch and listen

Actual result: Multiple notifications pop up and play for the single multi-attachment message
Expected result: One notification for the entire message

Device info

Device: Pixel 2 XL
Android version: 9.0
Signal version: 4.43.8

Link to debug log

https://debuglogs.org/f361233a881ce2219b0c22cdd0f65bc2893b12ab9d989fb6b6139890b28392d9

Related forum thread: https://community.signalusers.org/t/multiple-notifications-for-single-message-with-multiple-image-attachments/8532?u=herohtar

Start by reproducing the issue by sending a message with multiple images, then review the linked debug log for the notification flow. Done means one notification appears and plays for the entire multi-attachment message rather than one per image.