It is my understanding that setting an environment varialbe `TEST_AWS_ACCOUNT_ID` for localstack sets that as the AWS account for the user in localstack.

However, setting it does not actually change any ARNs. For example:

1. Start localstack using `TEST_AWS_ACCOUNT_ID="111111111111" DEBUG=1 localstack start`
2. Deploy anything with an ARN (in this example I deployed a lambda)
3. Check the ARN. Example output for lambda:
```json
$ awslocal lambda list-functions
{
    "Functions": [
        {
            "FunctionName": "localtest-local-hello",
            "FunctionArn": "arn:aws:lambda:us-east-1:000000000000:function:localtest-local-hello",
            "Runtime": "nodejs10.x",
            "Role": "test_role",
            "Handler": "handler.hello",
            "CodeSize": 3077,
            "Description": "",
            "Timeout": 6,
            "MemorySize": 1024,
            "LastModified": "2019-11-06T06:43:53.451+0000",
            "CodeSha256": "V77gR13o90ET7+XquXBBc3Rxr1qDu1bE7S+A0Wbx5ys=",
            "Version": "$LATEST",
            "TracingConfig": {
                "Mode": "PassThrough"
            },
            "RevisionId": "3d4ed679-c1a9-4b7e-ad9e-f27e8543c5e9"
        }
    ]
}
```

ARN is still 000000000000
elif resource_type == 'Lambda::Version':
            name = resource_props.get('FunctionName')
            if not name:
                return None
            func_name = aws_stack.lambda_function_name(name)
            func_version = name.split(':')[7] if len(name.split(':')) > 7 else '$LATEST'
            versions = aws_stack.connect_to_service('lambda').list_versions_by_function(FunctionName=func_name)
            return ([v for v in versions['Versions'] if v['Version'] == func_version] or [None])[0]
        elif resource_type == 'Lambda::EventSourceMapping':
            resource_id = resource_props['FunctionName'] if resource else resource_id
            source_arn = resource_props.get('EventSourceArn')
            resource_id = resolve_refs_recursively(stack_name, resource_id, resources)
            source_arn = resolve_refs_recursively(stack_name, source_arn, resources)
            if not resource_id or not source_arn:
                raise Exception('ResourceNotFound')
            mappings = aws_stack.connect_to_service('lambda').list_event_source_mappings(
                FunctionName=resource_id, EventSourceArn=source_arn)
            mapping = list(filter(lambda m:
                m['EventSourceArn'] == source_arn and m['FunctionArn'] == aws_stack.lambda_function_arn(resource_id),
                mappings['EventSourceMappings']))
            if not mapping:
                raise Exception('ResourceNotFound')
            return mapping[0]
        elif resource_type == 'DynamoDB::Table':
            resource_id = resource_props['TableName'] if resource else resource_id
            return aws_stack.connect_to_service('dynamodb').describe_table(TableName=resource_id)
        elif resource_type == 'ApiGateway::RestApi':
            apis = aws_stack.connect_to_service('apigateway').get_rest_apis()['items']
            resource_id = resource_props['Name'] if resource else resource_id
            result = list(filter(lambda api: api['name'] == resource_id, apis))