refactor taskchampion::server into a module with submodules

taskchampion/src/lib.rs

@@ -37,6 +37,3 @@ pub use task::{Task, TaskMut};
 
 /// Re-exported type from the `uuid` crate, for ease of compatibility for consumers of this crate.
 pub use uuid::Uuid;
-
-#[cfg(test)]
-pub(crate) mod testing;