minor rework and filter dimensions

internal/entity/dimension.go

@@ -49,7 +49,15 @@ type Dimension struct {
 	Kind  DimensionKind
 }
 
+func (d Dimension) IsZero() bool {
+	return d.Value == 0
+}
+
 func (d Dimension) MarshalText() ([]byte, error) {
+	if d.Value == 0 && d.Kind == DimensionKindUnspecified {
+		return nil, nil
+	}
+
 	value := strconv.FormatFloat(d.Value, 'f', 4, 64) + " " + d.Kind.String()
 	return []byte(value), nil
 }
@@ -114,10 +122,14 @@ func ParseDimention(value string, locale DimensionLocale) (Dimension, error) {
 	return out, nil
 }
 
-func NewMilimeterDimension(value float64) Dimension {
+func NewCentimeterDimensionOrEmpty(value float64) Dimension {
+	if value == 0 {
+		return Dimension{}
+	}
+
 	return Dimension{
 		Value: value,
-		Kind:  DimensionKindMilimeter,
+		Kind:  DimensionKindCentimeter,
 	}
 }