TEST: app use of phone storage space

[nanometrenat]

As Serval Chat is getting used more and more, and on devices that have very little storage space (several we were installing the app on recently were already notifying they were out of space) we need to make 100% sure that high message volumes through the mesh don't impact users' own normal phone usage.

In theory the Serval Chat app already handles this, but we need to ensure thorough testing is done:

• how it decides what packets to download/sync when there is not much space on the device
• does it reduce space used by Serval Chat when other apps/videos are subsequently added to the phone?

If there is already doco on business rules around what scenarios ought to be catered for them we can potentially help test this in NZ.

[lakeman]

Serval chat should try to maintain 100MB of free space by default. Checking every 30 minutes if more space needs to be reclaimed.