Tags attached to an IAM user are not saved. Create a user with attached tags. The response from the create user doesn't include the tags and when you run a GetUser the tags are not included.
```
aws-sdk-swift % aws --endpoint-url http://localhost:4593 iam create-user --user-name test-user --tags Key=test,Value=hello
```
produces output
```
{
    "User": {
        "Path": "/",
        "UserName": "test-user",
        "UserId": "peldynzrvm2tofi6nmmr",
        "Arn": "arn:aws:iam::000000000000:user/test-user",
        "CreateDate": "2019-10-23T08:46:31.305Z"
    }
}
```
The GetUser call produces exactly the same output
```
aws --endpoint-url http://localhost:4593 iam get-user --user-name test-user
```


I am running localstack as follows
```
docker run -d -p 4593:4593 -e SERVICES='iam' localstack/localstack
```
'Version': '2012-10-17',
            'Statement': {
                'Effect': 'Allow',
                'Action': 's3:ListBucket',
                'Resource': 'arn:aws:s3:::example_bucket'
            }
        }
        test_user_name = 'test-user'
        self.iam_client.create_user(UserName=test_user_name)
        response = self.iam_client.create_policy(
            PolicyName='test-policy',
            PolicyDocument=json.dumps(test_policy_document)
        )
        test_policy_arn = response['Policy']['Arn']
        self.assertIn(TEST_AWS_ACCOUNT_ID, test_policy_arn)
        self.iam_client.attach_user_policy(UserName=test_user_name, PolicyArn=test_policy_arn)
        attached_user_policies = self.iam_client.list_attached_user_policies(UserName=test_user_name)
        self.assertEqual(len(attached_user_policies['AttachedPolicies']), 1)
        self.assertEqual(attached_user_policies['AttachedPolicies'][0]['PolicyArn'], test_policy_arn)
        
        self.iam_client.detach_user_policy(
            UserName=test_user_name,
            PolicyArn=test_policy_arn
        )
        self.iam_client.delete_policy(
            PolicyArn=test_policy_arn
        )
        self.iam_client.delete_user(
            UserName=test_user_name
        )