Add documentation for input data id

dmnverifierapi/src/main/java/de/unikoblenz/fgbks/core/dmn/domain/ids/InputDataId.java

 package de.unikoblenz.fgbks.core.dmn.domain.ids;
 
+import de.unikoblenz.fgbks.core.dmn.domain.vdmn.VDmnInputData;
+
+/**
+ * A InputDataId id, representing the id of a {@link VDmnInputData}.
+ */
 @JsonIdentifier("ruleId")
 public class InputDataId extends AbstractId {
 
+  /**
+   * Create a new copy of the initialValue with the id value of the given Id object.
+   *
+   * @param initialValue the original id
+   */
   public InputDataId(InputDataId initialValue) {
     this(initialValue.getValue());
   }
 
+  /**
+   * Create new InputDataId with the id value of the initialValue.
+   *
+   * @param initialValue the value of the new id
+   */
   public InputDataId(String initialValue) {
     super(initialValue);
   }