feat(config): add metrics bind config to policy file with flag hack

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/config/metrics.go

@@ -0,0 +1,39 @@
+package config
+
+import "errors"
+
+var (
+	ErrInvalidMetricsConfig  = errors.New("config: invalid metrics configuration")
+	ErrNoMetricsBind         = errors.New("config.Metrics: must define bind")
+	ErrNoMetricsNetwork      = errors.New("config.Metrics: must define network")
+	ErrInvalidMetricsNetwork = errors.New("config.Metrics: invalid metrics network")
+)
+
+type Metrics struct {
+	Bind    string `json:"bind" yaml:"bind"`
+	Network string `json:"network" yaml:"network"`
+}
+
+func (m *Metrics) Valid() error {
+	var errs []error
+
+	if m.Bind == "" {
+		errs = append(errs, ErrNoMetricsBind)
+	}
+
+	if m.Network == "" {
+		errs = append(errs, ErrNoMetricsNetwork)
+	}
+
+	switch m.Network {
+	case "tcp", "tcp4", "tcp6", "unix": // https://pkg.go.dev/net#Listen
+	default:
+		errs = append(errs, ErrInvalidMetricsNetwork)
+	}
+
+	if len(errs) != 0 {
+		return errors.Join(ErrInvalidMetricsConfig, errors.Join(errs...))
+	}
+
+	return nil
+}