Add functionality to set pin code for Bluetooth

[Givemeurcookies]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
Currently Bluetooth can only be "protected" through setting pairing to 1 or 2 minutes and then stopping pairing. The default has open Bluetooth pairing and no way to set a pin code. I would like to have Hifiberry generate a pin code by default instead of having bluetooth open by default.

I've had a few incidents where neighbours have connected to Hifiberry through Bluetooth and blasted music when sleeping, so a way to protect it that was turned on by default would be nice.

Describe alternatives you've considered
I've considered turning off Bluetooth all together but it's nice being able to use bluetooth and sometimes I have people over that I'd like to share the speaker with. Being able to sharing a pin code would make this easier without having to go to a website.

Removing users that are unwanted but previously have paired also requires using SSH to the Hifiberry to remove their entry from the bluetooth daemon, an easier way to configure this would be nice.

Additional context
I found a related forum post: https://support.hifiberry.com/hc/en-us/community/posts/360009540657-HiFiBerry-OS-Bluetooth-Pin-Code