When creating the following bucket notification configuration:
```json
{
    "QueueConfigurations": [
        {
            "Id": "some-id",
            "QueueArn": "arn:aws:sqs:eu-central-1:123456789:my-queue",
            "Events": [
                "s3:ObjectCreated:*"
            ],
            "Filter": {
                "Key": {
                    "FilterRules": [
                        {
                            "Name": "Prefix",
                            "Value": "path/to/folder/"
                        },
                        {
                            "Name": "Suffix",
                            "Value": ".json"
                        }
                    ]
                }
            }
        }
    ]
}
```
and adding some files to S3, I get the following errors from localstack:

```
localstack.services.s3.s3_listener: Unknown filter name: "Prefix"
localstack.services.s3.s3_listener: Unknown filter name: "Suffix"
```

When I change the FilterRule names from "Prefix" to "prefix" and "Suffix" to "suffix", everything works. AWS supports the capitalised name, so this looks like a bug in localstack.
return filters.get('S3Key', filters.get('Key', {}))
def prefix_with_slash(s):
    return s if s[0] == '/' else '/%s' % s
def get_event_message(event_name, bucket_name, file_name='testfile.txt', version_id=None, file_size=1024):
    
    bucket_name = normalize_bucket_name(bucket_name)
    return {
        'Records': [{
            'eventVersion': '2.0',
            'eventSource': 'aws:s3',
            'awsRegion': aws_stack.get_region(),
            'eventTime': timestamp(format=TIMESTAMP_FORMAT_MILLIS),
            'eventName': event_name,
            'userIdentity': {
                'principalId': 'AIDAJDPLRKLG7UEXAMPLE'
            },
            'requestParameters': {
                'sourceIPAddress': '127.0.0.1'  
            },
            'responseElements': {
                'x-amz-request-id': short_uid(),