loki: Add role+playbook for Grafana Loki

The current Grafana Loki server, *loki0.pyrocufflink.blue*, runs Fedora
CoreOS and is managed by Ignition and *cfg*.  Since I have declared
*cfg* a failed experiment, I'm going to re-deploy Loki on a new VM
running Fedora Linux and managed by Ansible.

The *loki* role installs Podman and defines a systemd-managed container
to run Grafana Loki.

roles/loki/files/loki.container

@@ -0,0 +1,25 @@
+# vim: set ft=systemd :
+[Unit]
+Description=Grafana Loki
+After=network-online.target
+Wants=network-online.target
+StartLimitIntervalSec=1m
+StartLimitBurst=60
+
+[Service]
+ExecStartPre=/bin/install -o 10001 -g 10001 -d %S/%P
+ExecStartPre=/bin/chcon -t container_file_t %S/%P
+ExecReload=/usr/bin/podman kill --cidfile=%t/%N.cid --signal HUP
+TimeoutStartSec=5m
+Restart=always
+RstartSec=1s
+
+[Container]
+Image=docker.io/grafana/loki:2.9.4
+Exec=-config.file=/etc/loki/config.yml
+Volume=%S/%P:/var/lib/loki:rw
+Volume=/etc/loki:/etc/loki:ro
+Network=host
+
+[Install]
+WantedBy=multi-user.target