feat: add :51090/metrics endpoint with Prometheus metrics listening on machine IP (#304)

Signed-off-by: Miek Gieben <miek@miek.nl>
Co-authored-by: Pasha Sviderski <me@psviderski.name>

cmd/uncloudd/main.go

@@ -11,6 +11,7 @@ import (
 	"github.com/psviderski/uncloud/internal/daemon"
 	"github.com/psviderski/uncloud/internal/log"
 	"github.com/psviderski/uncloud/internal/machine"
+	"github.com/psviderski/uncloud/internal/metrics"
 	"github.com/psviderski/uncloud/internal/version"
 	"github.com/spf13/cobra"
 )
@@ -46,6 +47,8 @@ func main() {
 	cmd.AddCommand(newDialStdioCommand())
 	cmd.AddCommand(newVersionCommand())
 
+	metrics.Version.WithLabelValues(version.String()).Set(1)
+
 	// ctx is canceled when the daemon command is interrupted.
 	ctx, cancel := context.WithCancel(context.Background())