[6.x] Add the exceptionContext method to the exception handler

[AbdelElrafa]

This PR will add the exceptionContext method to the exception handler to allow exception specific data to be added to the logging context.

Currently if you need to get context off of an exception to pass it to the logger you would need to override the whole report method and do it there.

Adding this method allows us to add context off of an exception by simply implementing the method in the applications Handler class. This is not a breaking change.

Example:

throw (new CustomException())->setCustomProperty('foo');

// App/Exceptions/Handler.php
protected function exceptionContext(Exception $e)
{
    if ($e instanceof CustomException) {
        return ['custom_context' => $e->getCustomProperty()];
    }
}

Now the logger can get the custom exception context and handle it just like it handles the other context.

[GrahamCampbell]

I think this would be best aimed at Laravel 7. ;)

[AbdelElrafa]

@GrahamCampbell Since it's not a breaking change I thought it should go in 6.x. Why should it target 7?

[GrahamCampbell]

Because the exception handler has already changed in 7.x, and I don't see the rush to get this into 6.x.

[GrahamCampbell]

That is, if this is merged at all. I'm not sure it's actually worth adding into the core, since this can already be achieved within apps.

[AbdelElrafa]

I submitted another PR to 7.x (#30784). I think it can still be merged into 6.x so I'll keep this open to see what Taylor says.

As for "this can already be achieved within apps", in my description I did mention that it can be achieved by overriding the whole report method, which isn't ideal for a app because it can make future updates problematic when something in the report method changes and they are overriding the whole method in their handler. Adding the exceptionContext method allows users a portal into adding context with the exception as a reference. Where as now they only have a portal to add context without access to the exception.