Protect group from license borrowing

[izendegi]

On this PR we

• Add a new setting to select the Zoom group to protect
• When recycling licenses, avoid removing license from users belonging to the protected group

[jrchamp]

This is a nice idea to help avoid unwanted reassignment. A few suggestions to help minimize the negative impacts on users who are not using groups or reassignment.

[jrchamp]

Thank you for all of your timely updates! This is very nice and should help users who needs this functionality. After applying the suggested changes, please make sure that it is still working as expected on your system (as I believe you may be one of the users of this functionality).

[izendegi]

Hi, @jrchamp

We've been using the original code for more than a year but haven't tested these last changes extensively (I'm on a leave for a couple of weeks), so please give me some weeks to test them and refine if needed.