Improve documentation on cast and default

[q-wertz]

Currently it is not clear from the documentation when using default together with cast, whether

1. the default value has to be given as string/int/etc. and the cast is done on it
2. the default value has to be given in the correct type
3. It doesn't matter

e.g.

import enum

import dynaconf as dc

class VisCheck(enum.StrEnum):
    NONE = enum.auto()
    A = enum.auto()
    B = enum.auto()


# Variant 1
dc.Validator(
    "VISIBILITY_CHECK",
    default="a",
    cast=VisCheck,
)

# Variant 2
dc.Validator(
    "VISIBILITY_CHECK",
    default=VisCheck.A,
    cast=VisCheck,
)

It would be nice to have a hint in the docs :)

EDIT: Wrong default type in Variant 2 (typo)

[pedro-psb]

Hey @q-wertz , option 1 is correct, cast is called for defaults.
Agreed that this can be more clear in the docs!

[q-wertz]

Not sure if I oversee something, but it looks like both solutions work in my case.
When I do not have the value in my config file, the default VisCheck.A is in the settings. When I set it to an object with invalid type (e.g. np.random.default_rng()) it fails with

Generator(PCG64) at 0x7F64087CF840 is not a valid VisCheck

For me from "user" view it looks like both variants are equivalent 😅

[pedro-psb]

Yeah, I guess they are equivalent because the casting function will usually bypass the value when called over an already casted value (like VisCheck(VisCheck('a'))).
We can say that it's usually equivalent, but I suggest describing that the cast is called for defaults.