Use GCP Application Default Credentials

[LincolnRychecky]

@mondora

The middleware should also have support for using application default credentials rather than passing a service account directly to the middleware as part of the config.

I have made the addition on my end and would like to open the PR for you, but it appears that your repo security rules forbid me from doing so.

If you can relax the rules I will open the PR for you to review!

[WilliamSoler]

@mondora

The middleware should also have support for using application default credentials rather than passing a service account directly to the middleware as part of the config.

I have made the addition on my end and would like to open the PR for you, but it appears that your repo security rules forbid me from doing so.

If you can relax the rules I will open the PR for you to review!

I am struggling to make the middleware work with ADC please could you post your code here or in a Gist so everyone can use it, since the repository author is not responding.