Facilitate debugging on connection failure

[hadrienk]

When setting up the module, I had a lot of trouble with the GOOGLE_APPLICATION_CREDENTIAL environment. The reason was some CI/CD details, but it would have saved me a lot of time to have some sort of diagnostic when the connection fails.

I am thinking:

• Display the GOOGLE_APPLICATION_CREDENTIAL.
  • If value present, open the file. Report IO errors
    • Try parsing the file's content. Report errors (without displaying the value though)
    • If no error, display a hash value of the content on debug

[gkatzioura]

You can do so if you use -X on maven. It actually displays all the logs

[gkatzioura]

mvn -X deploy