Clean up re-exports

[shinghim]

After #668 merges, move reexports to the core module

In a follow up, all of these internal crate re-exports can be done inside core/mod.rs, and then something like

#[cfg(feature = "_core")]
pub use crate::core::*;

#668 (comment)

[DanGould]

Additionally, visibility of core module be pub(crate). It's not intended to be part of the public api. Public api should be accessed behind payjoin::, payjoin::v1, payjoin::v2, etc. _core Is just a folder to put common state machinery.

[zealsham]

i want to work on this

[DanGould]

Go for it. Great issue to work on. bech32, error_codes, hpke, into_url, io, ohttp, output_substitution, persist, and request modules are all under consideration for this move.

[zealsham]

@DanGould just to be sure i get what you mean, we are moving bech32, error_codes, hpke, into_url, io, ohttp, output_substitution, persist, and request in to core and make them crate only for a cleaner public api . Already working on it this way .

[DanGould]

You will see the _core feature behind which there are many modules. I would like to be able clean up lib.rs so that everything enabled by core is all behind a single feature flag instead of many instances of the feature flag, using the syntax below:

#[cfg(feature="_core")]
pub use crate::core::*;

The precise modules which should be referenced in core/mod.rs are those which are imported when the feature="_core" is enabled currently in lib.rs. The submodule files e,g. request.rs would then be git mv into the core folder. Their visibility must be unchanged