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
```
if response.content:
            
            self._fix_account_id(response)
            
            self._fix_date_format(response)
            
            response.headers['content-length'] = str(len(response._content))
    def _fix_date_format(self, response):
        """ Normalize date to format '2019-06-13T18:10:09.1234Z' """
        pattern = r'<CreateDate>([^<]+) ([^<+]+)(\+[^<]*)?</CreateDate>'
        replacement = r'<CreateDate>\1T\2Z</CreateDate>'
        self._replace(response, pattern, replacement)
    def _fix_account_id(self, response):
        return aws_stack.fix_account_id_in_arns(
            response, existing=MOTO_ACCOUNT_ID, replace=TEST_AWS_ACCOUNT_ID)
    def _reset_account_id(self, data):
        """ Fix account ID in request payload. All external-facing responses contain our
            predefined account ID (defaults to 000000000000), whereas the backend endpoint
            from moto expects a different hardcoded account ID (123456789012). """
        return aws_stack.fix_account_id_in_arns(
            data, colon_delimiter='%3A', existing=TEST_AWS_ACCOUNT_ID, replace=MOTO_ACCOUNT_ID)
    def _replace(self, response, pattern, replacement):
        content = to_str(response.content)
        response._content = re.sub(pattern, replacement, content)
UPDATE_IAM = ProxyListenerIAM()