net/freeradius - custom default vlan-ID for mikrotik attributes

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Before you add a new report, we ask you kindly to acknowledge the following:

• I have read the contributing guide lines at https://github.com/opnsense/plugins/blob/master/CONTRIBUTING.md
• I have searched the existing issues, open and closed, and I'm convinced that mine is new.

I found these issues with a similar topic:

1. https://github.com/opnsense/plugins/issues/672 and https://github.com/opnsense/plugins/issues/673

2. https://github.com/opnsense/plugins/pull/2566

3. https://github.com/opnsense/plugins/issues/2722

• When the request is meant for an existing plugin, I've added its name to the title.

Is your feature request related to a problem? Please describe.
I use the mikrotik vlan attributes in opnsense from (1) and it works as expected.
If I activate the checkbox for the VLAN-fallback from (2) all users without an entry in the radius database were assigned to my management-VLAN. I expect the reason ist the special Mikrotik VLAN attribute.
Is there also a way to assign a default VLAN id to a Mikrotik AP?

Describe the solution you'd like
I think it is only necessary to add a query in the users template to change the parameter for the fallback VLAN if the mikrotik attributes and the vlan fallback are activated in /ui/freeradius/general/index

I hope my explaination is clear and comprehensible.

Describe alternatives you've considered

• a solution similar to the dhcp option in /ui/dnsmasq/settings#dhcpoptions to create every kind of parameter you want
• Using a extern radius for auth a txt config in the worst case

Additional context
nothing for the moment, please ask if need some

Start at the FreeRADIUS general settings entry point, /ui/freeradius/general/index, and the users template mentioned in the request; compare the existing VLAN-fallback and MikroTik attribute handling. Confirm the desired default VLAN behavior for both options and verify that users without a RADIUS database entry receive the configured VLAN.