MessageAction for cognito admin_create_user is now handled

If an invitation is attempted to be reset to a pool we validate that the user is indeed already in the pool else we raise a UserNotFoundException to match AWS behaviour

tests/test_cognitoidp/test_cognitoidp.py

@@ -911,6 +911,55 @@ def test_admin_create_existing_user():
     caught.should.be.true
 
 
+@mock_cognitoidp
+def test_admin_resend_invitation_existing_user():
+    conn = boto3.client("cognito-idp", "us-west-2")
+
+    username = str(uuid.uuid4())
+    value = str(uuid.uuid4())
+    user_pool_id = conn.create_user_pool(PoolName=str(uuid.uuid4()))["UserPool"]["Id"]
+    conn.admin_create_user(
+        UserPoolId=user_pool_id,
+        Username=username,
+        UserAttributes=[{"Name": "thing", "Value": value}],
+    )
+
+    caught = False
+    try:
+        conn.admin_create_user(
+            UserPoolId=user_pool_id,
+            Username=username,
+            UserAttributes=[{"Name": "thing", "Value": value}],
+            MessageAction="RESEND",
+        )
+    except conn.exceptions.UsernameExistsException:
+        caught = True
+
+    caught.should.be.false
+
+
+@mock_cognitoidp
+def test_admin_resend_invitation_missing_user():
+    conn = boto3.client("cognito-idp", "us-west-2")
+
+    username = str(uuid.uuid4())
+    value = str(uuid.uuid4())
+    user_pool_id = conn.create_user_pool(PoolName=str(uuid.uuid4()))["UserPool"]["Id"]
+
+    caught = False
+    try:
+        conn.admin_create_user(
+            UserPoolId=user_pool_id,
+            Username=username,
+            UserAttributes=[{"Name": "thing", "Value": value}],
+            MessageAction="RESEND",
+        )
+    except conn.exceptions.UserNotFoundException:
+        caught = True
+
+    caught.should.be.true
+
+
 @mock_cognitoidp
 def test_admin_get_user():
     conn = boto3.client("cognito-idp", "us-west-2")