Persistent keepalive setting not configured on simple interface with systemd-networkd provider

[sid3windr]

Affected Puppet, Ruby, OS and module versions/distributions

• Puppet: 5.5
• Ruby: 2.5
• Distribution: Debian
• Module version: 2.2.0

How to reproduce (e.g Puppet code you use)

wireguard::interface {
    'wg0':
      manage_firewall      => false,
      endpoint             => '10.0.0.1:51820',
      dport                => 51820,
      addresses            => [{'Address' => '192.168.0.1/24'},],
      persistent_keepalive => 25,
      public_key           => '<key>';
}

What are you seeing

Persistent keepalive set to 0 on the interface.

What behaviour did you expect instead

Persistent keepalive configured to 25 seconds on the interface.

Output log

[NetDev]
Name=wg0
Kind=wireguard

[WireGuard]
PrivateKeyFile=/etc/wireguard/wg0
ListenPort=51820

[WireGuardPeer]
PublicKey=<key>
Endpoint=10.0.0.1:51820
PersistentKeepalive=0
AllowedIPs=fe80::/64
AllowedIPs=fd00::/8
AllowedIPs=0.0.0.0/0

Any additional information you'd like to impart

[sid3windr]

n.b. Putting the persistent_keepalive directive inside a peers block together with the public_key and endpoint makes it work as expected.