Adds fromValue method to EntityType

Signed-off-by: Darshit Chanpura <[email protected]>

server/src/main/java/org/opensearch/accesscontrol/resources/EntityType.java

@@ -8,6 +8,11 @@
 
 package org.opensearch.accesscontrol.resources;
 
+import java.util.Arrays;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
 /**
  * This enum contains the type of entities a resource can be shared with.
  *
@@ -19,6 +24,9 @@ public enum EntityType {
     ROLES("roles"),
     BACKEND_ROLES("backend_roles");
 
+    private static final Map<String, EntityType> VALUE_MAP = Arrays.stream(values())
+        .collect(Collectors.toMap(EntityType::toString, Function.identity()));
+
     private final String value;
 
     EntityType(String value) {
@@ -29,4 +37,12 @@ public enum EntityType {
     public String toString() {
         return value;
     }
+
+    public static EntityType fromValue(String value) {
+        EntityType type = VALUE_MAP.get(value);
+        if (type == null) {
+            throw new IllegalArgumentException("No enum constant with value: " + value);
+        }
+        return type;
+    }
 }