do tag to string conversion in StringCompressor instead of Tag

pdb-api/src/main/java/org/lucares/pdb/api/StringCompressor.java

@@ -51,4 +51,12 @@ public class StringCompressor {
         return new Tag(f, v);
     }
 
+    public String getKeyAsString(final Tag tag) {
+        return get(tag.getKey());
+    }
+
+    public String getValueAsString(final Tag tag) {
+        return get(tag.getValue());
+    }
+
 }

pdb-api/src/main/java/org/lucares/pdb/api/Tag.java

@@ -38,21 +38,13 @@ public class Tag implements Comparable<Tag> {
         return field;
     }
 
-    public String getKeyAsString() {
-        return Tags.STRING_COMPRESSOR.get(field);
-    }
-
     public int getValue() {
         return value;
     }
 
-    public String getValueAsString() {
-        return Tags.STRING_COMPRESSOR.get(value);
-    }
-
     @Override
     public String toString() {
-        return Tags.STRING_COMPRESSOR.get(field) + "=" + Tags.STRING_COMPRESSOR.get(value);
+        return field + "=" + value;
     }
 
     @Override

pdb-api/src/main/java/org/lucares/pdb/api/Tags.java

@@ -207,15 +207,6 @@ public class Tags implements Comparable<Tags> {
         return String.valueOf(tags);
     }
 
-    public String toCsv() {
-        final List<String> tagsAsStrings = new ArrayList<>();
-        for (final Tag tag : tags) {
-            tagsAsStrings.add(tag.getKeyAsString() + "=" + tag.getValueAsString());
-        }
-
-        return String.join(",", tagsAsStrings);
-    }
-
     @Override
     public int hashCode() {
         if (hashCode == 0) {