Adds possibility to extract a taxonomy from taxonomic path included in sequence files

pkg/obiiter/extract_taxonomy.go

@@ -0,0 +1,18 @@
+package obiiter
+
+import "git.metabarcoding.org/obitools/obitools4/obitools4/pkg/obitax"
+
+func (iterator *IBioSequence) ExtractTaxonomy() (taxonomy *obitax.Taxonomy, err error) {
+
+	for iterator.Next() {
+		slice := iterator.Get().Slice()
+
+		taxonomy, err = slice.ExtractTaxonomy(taxonomy)
+
+		if err != nil {
+			return
+		}
+	}
+
+	return
+}