refactor: service

[chesedo]

Make shuttle_service::Service easier to implement by users

Breaking changes

• Axum service no longer use the SyncWrapper shim Maybe after deployer no longer has locks
• declare_service! no longer exists. #[shuttle_service::main] should fill all needs
• Any custom services need to change as follow:
  • Remove the build() method
  • bind() changed to the following

    async fn bind(mut self: Box<Self>, addr: SocketAddr) -> Result<(), shuttle_service::Error>;

    These changes are:
    • add async
    • remove the ref (&) on self
    • add : Box<Self> to self
    • change the Ok variant of the return result to ()
  • Remove the IntoService impl
  • (Optional) drop the async_trait dependency and use shuttle_service::async_trait instead

Example custom service

use shuttle_service::{Error, Service};

#[derive(Clone)]
pub struct MyService;

#[shuttle_service::async_trait]
impl Service for MyService {
    async fn bind(
        mut self: Box<Self>,
        _addr: std::net::SocketAddr,
    ) -> Result<(), shuttle_service::error::Error> {
        println!("service is binding");
        Ok(())
    }
}

#[shuttle_service::main]
async fn shuttle() -> Result<MyService, Error> {
    Ok(MyService {})
}

[nodard]

Task linked: CU-2ghbe5d Can't return a custom impl of shuttle_service::Service from shuttle::main

[brokad]

LGTM.

Nit which may help newcomers to this: StateBuilder<T> is basically ServiceBuilder<T: Service>. I wonder if we should document these internal types to make the crate more readable?