As an enhancement to https://github.com/localstack/localstack/pull/1194

It would be really helpful to send the Lambda name, either as data, a header, or as part of the URL.

At code location: https://github.com/localstack/localstack/blob/03c6f4bf250edd18eb818ed65090f508636b0bff/localstack/services/awslambda/lambda_api.py#L696

I can likely open a PR to handle this given some feedback on the feature and potential design.

Right now all I see is the following (using `npx http-echo-server`):
```
[socket#8] event: data
--> POST / HTTP/1.1
--> Host: 192.168.1.x:3000
--> User-Agent: python-requests/2.22.0
--> Accept-Encoding: gzip, deflate
--> Accept: */*
--> Connection: keep-alive
--> Content-Length: 9
--> Content-Type: application/x-www-form-urlencoded
-->
-->
[socket#8] event: data
--> Name=test
```
batch_size = check_batch_size_range(source_arn, batch_size)
    mapping = {
        'UUID': str(uuid.uuid4()),
        'StateTransitionReason': 'User action',
        'LastModified': float(time.mktime(datetime.utcnow().timetuple())),
        'BatchSize': batch_size,
        'State': 'Enabled' if enabled is True or enabled is None else 'Disabled',
        'FunctionArn': func_arn(function_name),
        'EventSourceArn': source_arn,
        'LastProcessingResult': 'OK',
        'StartingPosition': LAMBDA_DEFAULT_STARTING_POSITION
    }
    event_source_mappings.append(mapping)
    return mapping
def update_event_source(uuid_value, function_name, enabled, batch_size):
    for m in event_source_mappings:
        if uuid_value == m['UUID']:
            if function_name:
                m['FunctionArn'] = func_arn(function_name)
            batch_size = check_batch_size_range(m['EventSourceArn'], batch_size or m['BatchSize'])
            m['BatchSize'] = batch_size
            m['State'] = 'Enabled' if enabled is True else 'Disabled'
            m['LastModified'] = float(time.mktime(datetime.utcnow().timetuple()))
            return m
    return {}
def delete_event_source(uuid_value):