refactor: use new checker types

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

lib/checker/headermatches/useragent.go

@@ -1 +1,35 @@
 package headermatches
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/TecharoHQ/anubis/lib/checker"
+)
+
+func ValidUserAgent(valueRex string) error {
+	fc := fileConfig{
+		Header:     "User-Agent",
+		ValueRegex: valueRex,
+	}
+
+	return fc.Valid()
+}
+
+func NewUserAgent(valueRex string) (checker.Interface, error) {
+	fc := fileConfig{
+		Header:     "User-Agent",
+		ValueRegex: valueRex,
+	}
+
+	if err := fc.Valid(); err != nil {
+		return nil, err
+	}
+
+	data, err := json.Marshal(fc)
+	if err != nil {
+		return nil, err
+	}
+
+	return Factory{}.Build(context.Background(), json.RawMessage(data))
+}