[8.x] Give a more meaningul message when route parameters are missing

[simensen]

The message for UrlGenerationException when parameters are missing is a nice start, but knowing which parameters are missing can be a huge help in figuring out where something is broken. Especially if a route has multiple possible parameters. Which parameter is actually missing? Are more than one missing? Now we'll know!

For example, say a developer is presented with the following exception message:

Missing required parameters [Route: admin.client.form.show] [URI: admin/client/{client}/form/{webform}]

It would lead them to their controller which might look something like this:

$connectionRequest->serviceUrl = route('admin.client.form.show', [
    'client' => $connectionRequest->client,
    'webform' => $serviceIntake,
]);

... it is not immediately obvious where to start. Is it that the $connectionRequest doesn't have a client? Or is the $serviceIntake set to null for some reason? Or are they both having issues?

With this PR, the exception message would change to one of the following:

• Missing required parameters [Route: admin.client.form.show] [URI: admin/client/{client}/form/{webform}] [Missing Parameters: client, webform].

• Missing required parameter [Route: admin.client.form.show] [URI: admin/client/{client}/form/{webform}] [Missing Parameter: client].

• Missing required parameter [Route: admin.client.form.show] [URI: admin/client/{client}/form/{webform}] [Missing Parameter: webform].

This feedback will save the developer a lot of time trying to figure out which parameters are missing so they can get right to fixing the issue instead of digging more to figure out which parameter is actually causing the problem.

---

Originally targeted 8.x with this PR, but realized it can go all the way back to 6.x, too. Let me know if you'd like me to retarget another branch or if there is anything I can do to help ensure this makes it into the most versions possible if it is accepted. :)

[taylorotwell]

Hey Beau, would you mind sending this to 8.x?

[simensen]

@taylorotwell No problem. I fixed a styleci issue, rebased, and changed the base branch on GitHub. Looks like the tests are all queued again.

[driesvints]

We'll have to be aware that this is technically a breaking change for people extending this exception and method.

[GrahamCampbell]

We could just re-target this PR at master. It's not long till another release anyway (indeed, it never really is, with the 6 month release cycle).

[simensen]

I'm happy with whatever. :)