[EOSC DUMP SCHEMA] added description to some of the fields

dump-schema/src/main/java/eu/dnetlib/dhp/oa/model/Container.java

@@ -27,10 +27,13 @@ public class Container implements Serializable {
 	@JsonSchema(description = "Name of the journal or conference")
 	private String name;
 
+	@JsonSchema(description = "The issn")
 	private String issnPrinted;
 
+	@JsonSchema(description = "The eissn")
 	private String issnOnline;
 
+	@JsonSchema(description = "The lissn")
 	private String issnLinking;
 
 	@JsonSchema(description = "End page")