Add Support for Google Secret Manager as a Source

[Dresdn]

Original Credit: https://www.codingforentrepreneurs.com/blog/google-secrets-python-decouple-github-actions/

Working with Google Secret Manager, the config is provided back as a string. To support the format, a RepositoryString class has been created which parses a string in .env format.

[Dresdn]

@henriquebastos - if you're in agreement to support this, I can take some time to update the Readme with the new option.

[felciano]

I was just looking for this! Thanks for contributing @Dresdn I hope this gets accepted soon

[henriquebastos]

@Dresdn thank you for your contribution.

1. Is this literally the same as the RepositoryEnv minus opening the file?
2. Or is this a Google-specific string format?

In case of 1, it would be nice to refactor RepositoryEnv extending RepositoryString, but we can do it later.

In case of 2, maybe RepositoryString should be RepositoryGoogleManager or something more descriptive.

Wdyt?

[Dresdn]

Those are great ideas @henriquebastos, and apologize for being lazy and plopping in the class I used in my project.

For 1, I was trying not to make it specific to Google since it's a generic format, but looking at other secret managers, they seem to all manage them differently (some have dicts, some return one value at a time). Maybe just renaming it RepositoryGoogleSecretManager would be best.

For 2, should we create a BaseRepositoryDict or something that declares the __contains__() and __getitem__() and have RepositoryEnv and RepositoryGoogleSecretManager extend that? I'm probably over-thinking it, but the thought process would be other managers that use dicts.

Let me know your thoughts and I'll clean up the PR and add some documentation too.

[Dresdn]

This should be ready to go @henriquebastos (minus my default editor settings trying to change everything). I ended up just extending RepositoryEnv and renaming the class to better reflect the purpose.