Feature/session tracking

[mschadegg]

Goal

To implement Session tracking for the stability score in Bugsnag.

Design

It builds on top on my other pull request for V3 of the PHP SDK.
Its optional to use session tracking due to the implemented setting.

Changeset

I have added a checkbox to the settings page to allow session tracking to be toggled on/off.
I have implemented the session tracking functionality as early as possible with its own method maybeTrackSession.

Testing

I have manually tested in a test environment against a test project in bugsnag.

[agrzegorzewski]

Hi @mschadegg,
As mentioned here, we're working on updating the notifier.
Thanks for the contribution.

[mschadegg]

Thanks for the new release with the new version of the SDK.

This pull request, which introduce session tracking, was initially pulled in to the release, but later removed. It looks like the remove was unintended.
Was that intended or was it unintended?

If it was intended to remove it; why?

[hannah-smartbear]

Hi @mschadegg,

Unfortunately we weren't able to fully implement the session tracking change due to technical constraints, but you can still use session tracking by starting it manually as described here: https://docs.bugsnag.com/platforms/php/other/#session-tracking