feat(dotenv): Adding support for dotenv files

[chickencoding123]

This adds support for dotenv file format. It is accomplished by using dotenvy crate. There's an open issue asking for this feature here #16.

[coveralls]

Pull Request Test Coverage Report for Build 18750157020

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 64.846%

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Totals
Change from base Build 18169995909:	0.0%
Covered Lines:	950
Relevant Lines:	1465

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💛 - Coveralls

[epage]

Does this work as another FileFormat / Source? I suspect there is a lot of design overlap with Environment that we'd want to make this functionality on that.

[chickencoding123]

This is another FileFormat. You can see the usage from the tests (added snippet for ref. here). It is similar to existing file formats. Also dotenvy dependency will take care of the overlap, if any. However I ensured OS env take precedence as per existing file formats.

 let s = Config::builder()
        .add_source(config::File::from_str(
            r#"
                FOO=bar
                BAZ=qux
            "#,
            config::FileFormat::Dotenv,
        ))
        .build()
        .unwrap();

[epage]

FYI resolving conversations that aren't ready for it can make PR reviews more difficult on maintainers. You should be pretty confident that you understood the concern and responded to it as the maintainer expected to resolve it. That was not the case here.

Some traits of dotenv are

• Stringly typed (so is ini)
• Unstructured

Both of these characteristics are shared with Environment which has a lot of functionality for solving these problems. In fact, this is another form of environment variables! The only difference is it also shares some of the file loading characteristics of file formats.

[epage]

I've raised this (and other questions) at #16 (comment) as I prefer to work out high level designs in Issues rather than PRs.

[chickencoding123]

I've updated to strike a balance between dotenv ambitions and preferences of this repository.

[epage]

I'm not aware of any dotenv "ambitions" that come in conflict with "preferences of this repository". Also, for any "preferences" I'm giving, they are about fully supporting dotenv rather than doing it party way.

[epage]

Feel free to modify your commits for how they should be merged