Draft: Added conditional validation for complex relations

fixes https://gitlab.ruhr-uni-bochum.de/FDM/rdm-system/antleaf-projectmanagement/-/issues/187

hyrax/app/assets/javascripts/dataset_form.js

+$(document).on('change', '.complex_relation_section input:visible, .complex_relation_section select:visible', function() {
+  var is_required = false;
+
+  var $field_wrapper = $(this).closest('.complex_relation_section');
+  var $child_elements = $field_wrapper.find('input:visible, select:visible');
+
+  $child_elements.each(function(index, child){ 
+    if ($(child).val().length > 0){
+      is_required = true
+    }
+  });
+
+  is_required ? $child_elements.prop('required', true) : $child_elements.prop('required', false) 
+});
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