Report internal errors when serialization fails

[fractalwrench]

Goal

#570 added internal error reports for deserialization, which are delivered to Bugsnag when an unanticipated error occurred. This adds similar functionality for the serialization case, which will allow us to diagnose errors when writing files.

Changeset

• Moved delegate property to FileStore so that serialisation errors are captured for errors/session payloads
• Sent internal reports in two additional cases:
  • When copying an NDK report to the JVM directory fails
  • When serializing a JVM report to disk fails
• Captured the following additional diagnostic info in reports:

canRead // whether the file is readable
canWrite // whether the file is writable
exists // whether the file exists
usableSpace // the amount of usable space in bytes in the cache directory

[kattrali]

I left a few concerns inline though my biggest right now is how can this change be verified? Is it tested in some way already?

[fractalwrench]

I originally tested this by assembling a local artefact, altering the relevant code to always throw an exception, then checking on a local server that the payload was correct. I've also tested against our internal instance and verified the exceptions are picked up.

This doesn't seem like the sort of change that would be feasible to test in an automated way - at least, I can't think of a good way to achieve that.