[5.6] Add allowed ip's or networks to Maintenance Mode

[cesargb]

With this PR I can access to the App in maintenance mode from certain ip address or networks.

Example:

php artisan down --allow=127.0.0.1 --allow=192.168.0.0/16

[browner12]

Can you explain your use case? When is your App going into maintenance mode, and what do you need to see on your production app when it's in maintenance mode?

[m1kfb]

Fixing Data issues in production would be one use case, would be particularly useful for e-commerce instances changing promotional content.

[browner12]

ahh, so you're thinking like an https://apple.com shutting down its store when it adds new products?

[m1kfb]

Yeah, you and sort out product layouts, banners etc... without displaying to customers till it's ready. I don't currently require this functionality myself but could see it being useful.

[BrandonShar]

Nice idea. I always whitelist my own IP when I take a production site down. It's nice to be able to have a look around before turning everything back on.

[jdecode]

This feature (probably) allows for validating the changes (something on the lines of a "build checklist") on the live environment, before pulling down the maintenance shield (and, hopefully, allows triggering a rollback mechanism if any check fails from the build checklist).