introduced a new custom file format used for backup and ingestion

The new file format reduces repetition, is easy to parse,
easy to generate in any language and is human readable.

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

@@ -7,6 +7,7 @@ import java.util.Set;
 import java.util.TreeSet;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
+import java.util.regex.Pattern;
 
 import org.lucares.collections.IntList;
 import org.lucares.collections.LongList;
@@ -198,6 +199,28 @@ 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);
+	}
+
+	public static Tags fromCsv(final String line) {
+
+		final TagsBuilder tagsBuilder = new TagsBuilder();
+		final String[] tagsAsString = line.split(Pattern.quote(","));
+
+		for (final String tagAsString : tagsAsString) {
+			final String[] keyValue = tagAsString.split(Pattern.quote("="));
+			tagsBuilder.add(keyValue[0], keyValue[1]);
+		}
+
+		return tagsBuilder.build();
+	}
+
 	@Override
 	public int hashCode() {
 		final int prime = 31;