Allow setting logger's format at runtime

[blisscs]

Hi,

Currently, I am having an issue that I can't set the format of the logger at runtime because the current implementation takes the format string from the module attribute which is set at compile time. With this pull request, we will be able to set the format at run time with the below code sample.

  middleware = [
    {Tesla.Middleware.Logger, format: "$method $url -> $status ($time ms)"}
    # ,... more middlewares
  ]

  client = Tesla.client(middleware)

[blisscs]

Hi @teamon,

I have been using tesla for some time now. I have a little issues in that i can't configure my logger's format at runtime. This merge request will help to resolve that. please help review this merge request, if you have any comments please let's me know

Thanks.
Suracheth

[blisscs]

Hi @teamon Please let's me know what do you think of this merge request to allow setting the format of logger at runtime.

[blisscs]

@thiamsantos I update the code to use pipe. Let's me know if you need other changes.

[teamon]

Perfect!