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
```
result = sqs_client.receive_message(QueueUrl=queue_url, MessageAttributeNames=['All'])
            self.assertGreater(len(result['Messages']), 0)
            msg_attrs = result['Messages'][0]['MessageAttributes']
            self.assertIn('RequestID', msg_attrs)
            self.assertIn('ErrorCode', msg_attrs)
            self.assertIn('ErrorMessage', msg_attrs)
        retry(receive_dlq, retries=8, sleep=2)
    def test_add_lambda_permission(self):
        iam_client = aws_stack.connect_to_service('iam')
        lambda_client = aws_stack.connect_to_service('lambda')
        
        action = 'lambda:InvokeFunction'
        sid = 's3'
        resp = lambda_client.add_permission(FunctionName=TEST_LAMBDA_NAME_PY, Action=action,
                                            StatementId=sid, Principal='s3.amazonaws.com',
                                            SourceArn=aws_stack.s3_bucket_arn('test-bucket'))
        self.assertIn('Statement', resp)
        
        policy = lambda_client.get_policy(FunctionName=TEST_LAMBDA_NAME_PY)['Policy']
        self.assertIsInstance(policy, six.string_types)
        policy = json.loads(to_str(policy))
        self.assertEqual(policy['Statement'][0]['Action'], action)
        self.assertEqual(policy['Statement'][0]['Sid'], sid)
        self.assertEqual(policy['Statement'][0]['Resource'], lambda_api.func_arn(TEST_LAMBDA_NAME_PY))
        
        policies = iam_client.list_policies(Scope='Local', MaxItems=500)['Policies']
        matching = [p for p in policies if p['PolicyName'] == 'lambda_policy_%s' % TEST_LAMBDA_NAME_PY]
        self.assertEqual(len(matching), 1)