matrix.archlinux.org: Configure static DNS via networking role

Hetzner DNS has been delaying many responses for 5 seconds, causing
outgoing federation work to pile up, almost running into OOM before we
noticed.

I don't know if were being throttled because federation makes a *lot* of
requests. Anyway, using Cloudflare DNS seems to solve it.

Enable DNSOverTLS for this because we can.

host_vars/matrix.archlinux.org/misc

 ---
 filesystem: btrfs
+static_dns: true
 wireguard_address: 10.0.0.15
 wireguard_public_key: QWkTL58mJd0+Lz5AvGVmbdSSk29y/W60WUdhTgyGLCk=

roles/networking/files/dns.conf

+[DHCPv4]
+UseDNS=false
+
+[DHCPv6]
+UseDNS=false
+
+[IPv6AcceptRA]
+UseDNS=false
+
+[Network]
+DNS=2606:4700:4700::1111#1dot1dot1dot1.cloudflare-dns.com
+DNS=2606:4700:4700::1001#1dot1dot1dot1.cloudflare-dns.com
+DNS=1.1.1.1#1dot1dot1dot1.cloudflare-dns.com
+DNS=1.0.0.1#1dot1dot1dot1.cloudflare-dns.com
+DNSOverTLS=true

roles/networking/tasks/main.yml

 ---
 - name: configure network (static)
-  template: src=10-static-ethernet.network.j2 dest={{ chroot_path }}/etc/systemd/network/10-static-ethernet.network owner=root group=root mode=0644
-  notify:
-    - restart networkd
+  block:
+    - name: install 10-static-ethernet.network
+      template: src=10-static-ethernet.network.j2 dest={{ chroot_path }}/etc/systemd/network/10-static-ethernet.network owner=root group=root mode=0644
+      notify:
+        - restart networkd
+
+    - name: create drop-in directory for 10-static-ethernet.network
+      file: path=/etc/systemd/network/10-static-ethernet.network.d state=directory owner=root group=root mode=0755
+
+    - name: configure static dns (static)
+      copy: src=dns.conf dest={{ chroot_path }}/etc/systemd/network/10-static-ethernet.network.d/dns.conf owner=root group=root mode=0644
+      notify:
+        - restart networkd
+      when: static_dns|default(false)
   when: not dhcp|default(false)
 
 - name: configure network (dhcp)
-  template: src=10-dhcp-ethernet.network.j2 dest={{ chroot_path }}/etc/systemd/network/10-dhcp-ethernet.network owner=root group=root mode=0644
-  notify:
-    - restart networkd
+  block:
+    - name: install 10-dhcp-ethernet.network
+      template: src=10-dhcp-ethernet.network.j2 dest={{ chroot_path }}/etc/systemd/network/10-dhcp-ethernet.network owner=root group=root mode=0644
+      notify:
+        - restart networkd
+
+    - name: create drop-in directory for 10-dhcp-ethernet.network
+      file: path=/etc/systemd/network/10-dhcp-ethernet.network.d state=directory owner=root group=root mode=0755
+
+    - name: configure static dns (dhcp)
+      copy: src=dns.conf dest={{ chroot_path }}/etc/systemd/network/10-dhcp-ethernet.network.d/dns.conf owner=root group=root mode=0644
+      notify:
+        - restart networkd
+      when: static_dns|default(false)
   when: dhcp|default(false)
 
 - name: create symlink to resolv.conf