Use cargo-deb to build a Debian package

This ships also a systemd service unit and a config file for
`/etc/default`

Cargo.toml

@@ -16,3 +16,14 @@ env_logger = "0.9"
 tokio = { version = "1.17", features = ["rt-multi-thread", "macros"] }
 axum = "0.5"
 clap = { version = "3.1", features = ["derive"] }
+
+[package.metadata.deb]
+extended-description = "Prometheus exporter for the MightyOhm Geiger Counter."
+section = "utility"
+maintainer-scripts = "debian/"
+systemd-units = { enable = true }
+assets = [
+    ["target/release/mightyohm-gc-exporter", "usr/bin/", "755"],
+    ["README.md", "usr/share/doc/mightyohm-gc-exporter/README", "644"],
+    ["debian/default", "etc/default/mightyohm-gc-exporter", "644"],
+]

debian/default

@@ -0,0 +1,10 @@
+ARGS=""
+
+# mightyohm-gc-exporter supports the following options:
+#  -a, --address <ADDRESS>            The IPv4 or IPv6 address where the metrics are served
+#                                     [default: 127.0.0.1]
+#  -b, --baud-rate <BAUD_RATE>        The baudrate of the serial connection [default: 9600]
+#  -p, --port <PORT>                  The port where the metrics are served [default: 9111]
+#  -s, --serial-port <SERIAL_PORT>    The port of the serial device, usually in '/dev/...'
+#                                     [default: /dev/serial0]
+#  -t, --timeout <TIMEOUT>            Timeout of the serial connection in ms [default: 1000]

debian/service

@@ -0,0 +1,11 @@
+[Unit]
+Description=MightyOhm Geiger Counter exporter
+
+[Service]
+Group=dialout
+Restart=always
+EnvironmentFile=/etc/default/mightyohm-gc-exporter
+ExecStart=/usr/bin/mightyohm-gc-exporter $ARGS
+
+[Install]
+WantedBy=multi-user.target