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
```
""" List functions
        ---
        operationId: 'listFunctions'
        parameters:
            - name: 'request'
              in: body
    """
    funcs = do_list_functions()
    result = {}
    result['Functions'] = funcs
    return jsonify(result)
@app.route('%s/functions/<function>' % PATH_ROOT, methods=['DELETE'])
def delete_function(function):
    """ Delete an existing function
        ---
        operationId: 'deleteFunction'
        parameters:
            - name: 'request'
              in: body
    """
    arn = func_arn(function)