Use OkHttpClient to download notification videos

[jpelgrom]

Summary

This PR fixes downloading notification videos from servers that have enabled TLS client certificate authentication, a bug reported in a comment on a related bug here.

The app will now handle the downloading so that it is possible to provide the necessary authentication, instead of asking the system to do it. The file is removed as soon as the frames are extracted.

Screenshots

n/a, notifications will show videos again instead of not including them

Link to pull request in Documentation repository

n/a

Any other notes

cc @Rogue136198, as you reported this bug I'd appreciate it if you could also verify that the change works

[Rogue136198]

Just tested and everything is working as expected.

I tested without mTLS and the performance seems to even be a bit better than before. Notifications appear noticeably faster now.

[jpelgrom]

I tested without mTLS

I'm confused, did you als test with mTLS? That is what was causing the bug after all.

[Rogue136198]

I tested without mTLS

I'm confused, did you als test with mTLS? That is what was causing the bug after all.

Oh yes! Sorry I should have been more clear. I tested with mTLS and it works flawlessly. Without mTLS was just for A/B testing on performance when I noticed it felt faster.