Add Optional to access mapper

types/mapper/access.go

@@ -8,6 +8,7 @@ import (
 
 type Access struct {
 	Fields   map[string]string
+	Optional bool
 }
 
 func (e Access) FromInternal(data map[string]interface{}) {
@@ -20,6 +21,9 @@ func (e Access) ToInternal(data map[string]interface{}) error {
 func (e Access) ModifySchema(schema *types.Schema, schemas *types.Schemas) error {
 	for name, access := range e.Fields {
 		if err := ValidateField(name, schema); err != nil {
+			if e.Optional {
+				continue
+			}
 			return err
 		}