Add AllowedIPs optional setting for peers about linguard

[jine]

Huh? The problem? It's not really a problem, more of an enhancement with more features (such as autocompletion of input subnets, common ones/previously used ones for instance).... ?

But yeah - thanks for the input on where the placeholder comes from!

I've also just updated the allowed ips above, we realized those before were actually wrong... :)

[jine]

Note that i'm adding both subnets and a list of IPs (/32s), having them in a "template" or / and auto-completed from previous peers would be best i think.

[jine]

Tunnel all traffic for the public internet over WG (exclude any/all local network subnets)

EDIT: CORRECTED 2021-11-22:
AllowedIPs = 1.0.0.0/8, 2.0.0.0/7, 4.0.0.0/6, 8.0.0.0/7, 11.0.0.0/8, 12.0.0.0/6, 16.0.0.0/4, 32.0.0.0/3, 64.0.0.0/3, 96.0.0.0/4, 112.0.0.0/5, 120.0.0.0/6, 124.0.0.0/7, 126.0.0.0/8, 128.0.0.0/3, 160.0.0.0/5, 168.0.0.0/8, 169.0.0.0/9, 169.128.0.0/10, 169.192.0.0/11, 169.224.0.0/12, 169.240.0.0/13, 169.248.0.0/14, 169.252.0.0/15, 169.255.0.0/16, 170.0.0.0/7, 172.0.0.0/12, 172.32.0.0/11, 172.64.0.0/10, 172.128.0.0/9, 173.0.0.0/8, 174.0.0.0/7, 176.0.0.0/4, 192.0.0.0/9, 192.128.0.0/11, 192.160.0.0/13, 192.169.0.0/16, 192.170.0.0/15, 192.172.0.0/14, 192.176.0.0/12, 192.192.0.0/10, 193.0.0.0/8, 194.0.0.0/7, 196.0.0.0/6, 200.0.0.0/5, 208.0.0.0/4, 224.0.0.0/4, ::/1, 8000::/2, c000::/3, e000::/4, f000::/5, f800::/6, fe00::/9, fec0::/10, ff00::/8

For instance, as the WG-android app does - is a hell of a config to copy and paste each time, that should definitely be an option aswell while creating peers.

EDIT: CORRECTED 2021-11-22:
I've updated the above string, we had missed a few nets (especially - it had 0.0.0.0/5 in the beginning which is incorrect...)
https://www.procustodibus.com/blog/2021/03/wireguard-allowedips-calculator/ is a great guideline.

[grishingr]

This is an unpleasant feature. This problem is solved by replacing the validators in the ipv4 field:
ipv4 = StringField("IPv4", validators=[DataRequired(), PeerIpValidator()],
render_kw={"placeholder": "0.0.0.0/32"})

In this class:
class PeerIpValidator