I've searched throughout the web with no joy. My background: I've got 16+ years in software (I'm out of it but not before I built some Android apps for myself).
My problem is that I'd like to reduce the amount of space used on my phone for old messages but I'd like to keep them available.
Something like an automated system that prunes old messages to off-site (cloud) storage but makes them available upon demand.
What I want, is a system that lets me keep my chats growing indefinitely while keeping only a specified amount of space used on the phone.