Added convenience method to check Role existance by string

src/main/java/org/gcube/oidc/D4ScienceMappings.java

@@ -1,5 +1,8 @@
 package org.gcube.oidc;
 
+import java.util.HashSet;
+import java.util.Set;
+
 public class D4ScienceMappings {
 
     public enum Role {
@@ -16,6 +19,8 @@ public class D4ScienceMappings {
         VRE_DESIGNER("VRE-Designer"),
         VRE_MANAGER("VRE-Manager");
 
+        private static Set<String> STRING_VALUES;
+
         private String str;
 
         Role(String str) {
@@ -25,6 +30,22 @@ public class D4ScienceMappings {
         public String asString() {
             return str;
         }
+
+        static {
+            STRING_VALUES = new HashSet<String>();
+            for (Role role : Role.values()) {
+                STRING_VALUES.add(role.asString());
+            }
+        }
+
+        public static Set<String> stringValues() {
+            return STRING_VALUES;
+        }
+
+        public static boolean exists(String role) {
+            return STRING_VALUES.contains(role);
+        }
+
     }
 
     public enum Scope {