Splitting Zitadel-rust project in sub crates

[fcenedes]

Hi there,

Major Changes, Possible Break
This PR is a first attempt to split the zitadel-rust crate into 3 crates :

• zitadel-rust : Workspace
• crates/zitadel : Helpers crate around Zitadel API, basically the former crate we all loved.
• crates/zitadel-gen : Build and generates GRPC stufs from zitadel as Rust Structs and Tonic clients
• crates/zitadel-examples: Various samples on how to use the zitadel crate

the zitadel-gen could be renamed zitadel-sys or whatever, but it should basicaly hold the same version as the zitadel version where the proto files are extracted.
The zitadel:: is properly re-exported, so if should have no impacts on downstream users

Minor Changes :
zitadel crate :

• Another little addition, is an helper method to introspect a JWT token locally instead of calling the instrospect endpoint against a Zitadel instance. Note this only work with 3 legs JWT tokens, not opaque one.
• Another modification is the ability to support arbitrary custom claims, letting the user of this crate to make his own impl
• One axum deps has been yanked, so the Cargo.toml just reflect that.

the CI/CD needs probably be reviewed and fixed to be aligned if this PR is accepted

Don't be shy, if i wrote crappy code, just let me know :-)

[fcenedes]

well i realise i dont pass some linting. Wonder if i should revert back to buf instead of trying to do it myself :-)

i will amend this pr. Buf actually solve a couple of problems.

Sorry

[buehler]

Will look into it on the weekend ;)
Splitting the code seems to be a good idea.

and yeah, buf has its perks ;) I learned that the hard way as well.

[buehler]

One question that comes to mind: why use a third crate for examples? As far as I know in Rust people show examples inside the crate. Those are not compiled when the crate is downloaded right?

[fcenedes]

no particular reason, i will move them back into the zitadel crate.
EDIT : now i remember, i took inspiration from https://github.com/apache/datafusion/tree/main/datafusion-examples
probably to have them isolated from the main crate..but anyway :)

[fcenedes]

you will have to exclude cargo clippy for the generated Tonic code.