[Issue] add subnet mask IP support for maintenance mode

[m2-assistant]

This issue is automatically created based on existing pull request: #28934: add subnet mask IP support for maintenance mode

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Description

Maintenance mode should accept IP ranges instead of separate IP's so that for instance you can add the whole range of your payment service provider or CDN etc...

Fixed Issues (if relevant)

1. PR add subnet mask IP support for maintenance mode #10570

Manual testing scenarios

1. run bin/magento maintenance:enable
2. run bin/magento maintenance:allow-ips 192.168.33.0/16 (for instance)
3. get access to the site

Mostly I am curious what you think about this kind of functionality and the use of darsyn/ip for this. I did take IPv6 into account.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)