Add a a way to specify descriptions and default values using dynaconf_validaors.toml

Hi, thank you for the library. It really improved the way I approach configuration files. Finally I have types and proper sections. What I am missing is schema: I would love to be able to enforce that some parameters are obligatory, their type and provide a description, also raise an exception if there is some unknown parameter is configured. I think I could use something like marshmallow for that, but if it is part of this library, it would be great for my use-cases. What do you think?

UPD: after looking at the docs more, I think validators would solve majority of our use-cases, but I don’t see a way to specify descriptions and default values in a nice way, so that they are automatically populated in our docs.

[rochacbruno]

Now we can define default values using validators, the validators.toml is still missing this support

Details here: https://www.dynaconf.com/validation/#providing-default-or-computed-values

We still need

• Define description/help for a setting value in the validator (or as a schema class)
• Support description, default in toml validator
• Add a way to generate initial settings file based on validator.

[rochacbruno]

thinking a bit more, in the same way we have .secrets. maybe we can add support for a special .defaults. file, so when it is present dynaconf loads it first.