misc (systemd): Add `systemd` units:

Add units for ``systemd`` to easily handle Libervia services on system-wide installation.

There is a service to run a single backend instance for all clients and components, and
another one if administrators prefer isolated instances. The latter one uses a systemd
template system.

misc/systemd/README.md

@@ -0,0 +1,9 @@
+# Libervia systemd units
+
+Here you'll find [systemd](https://systemd.io/) units to run Libervia:
+
+- `libervia-backend.service`: to be used when you run a single backend instance for all
+  components and clients (or for the main instance).
+- `libervia@.service`: a template for isolated backend instances. To be used for a
+  component, a dedicated backend for the web frontend, or any other isolated usage.
+- `libervia-web.service`: Libervia Web frontend.

misc/systemd/libervia-backend.service

@@ -0,0 +1,18 @@
+[Unit]
+Description=Libervia Backend
+Wants=network-online.target
+After=network.target network-online.target
+
+[Service]
+Type=exec
+User=libervia
+Group=libervia
+StateDirectory=libervia
+RuntimeDirectory=libervia
+Environment=XDG_RUNTIME_DIR=/run/libervia
+ExecStart=libervia-backend fg
+Restart=on-failure
+RestartSec=5s
+
+[Install]
+WantedBy=multi-user.target

misc/systemd/libervia-web.service

@@ -0,0 +1,18 @@
+[Unit]
+Description=Libervia Web
+Wants=network-online.target libervia-backend.service
+After=network.target network-online.target libervia-backend.service
+
+[Service]
+Type=exec
+User=libervia
+Group=libervia
+StateDirectory=libervia-web
+RuntimeDirectory=libervia-web
+Environment=XDG_RUNTIME_DIR=/run/libervia-web
+ExecStart=libervia-web fg
+Restart=on-failure
+RestartSec=5s
+
+[Install]
+WantedBy=multi-user.target

misc/systemd/libervia@.service

@@ -0,0 +1,19 @@
+[Unit]
+Description=Libervia %i (isolated)
+Wants=network-online.target
+After=network.target network-online.target
+
+[Service]
+Type=exec
+User=libervia
+Group=libervia
+StateDirectory=libervia
+RuntimeDirectory=libervia-%i
+Environment=XDG_RUNTIME_DIR=/run/libervia-%i
+Environment=LIBERVIA_ISOLATION=%i
+ExecStart=libervia-backend fg
+Restart=on-failure
+RestartSec=5s
+
+[Install]
+WantedBy=multi-user.target