Uncouple endpoint construction from routing

The result looks more clunky for binding it to a route but at least the
concerns are separate more strictly. This also removes the need for
duplicating the router utilities for methods.

examples/seeded_extractor.rs

@@ -1,5 +1,6 @@
 #![feature(async_await, futures_api)]
 
+use tide::Seeded;
 use tide::head::{NamedHeader, Header, SegmentName, Named};
 use http::header::{HeaderName, HeaderValue};
 
@@ -13,7 +14,7 @@ async fn display_number(nr: Named<i32>) -> String {
 
 fn main() {
     let mut app = tide::App::new(());
-    app.at("/").get_with(display_header, NamedHeader(HeaderName::from_static("user-agent")));
-    app.at("/numbered/{num}").get_with(display_number, SegmentName("num".into()));
+    app.at("/").get(Seeded(display_header, NamedHeader(HeaderName::from_static("user-agent"))));
+    app.at("/numbered/{num}").get(Seeded(display_number, SegmentName("num".into())));
     app.serve();
 }

src/lib.rs

@@ -29,7 +29,7 @@ pub use crate::{
     app::{App, AppData, Server},
     configuration::ExtractConfiguration,
     cookies::Cookies,
-    endpoint::Endpoint,
+    endpoint::{Endpoint, Seeded},
     extract::{Extract, ExtractSeed},
     middleware::Middleware,
     request::{Compute, Computed, Request},

src/router.rs

@@ -5,7 +5,7 @@ use std::sync::Arc;
 
 use crate::{
     configuration::Store,
-    endpoint::{BoxedEndpoint, Endpoint, Seeded},
+    endpoint::{BoxedEndpoint, Endpoint},
     Middleware,
 };
 use path_table::{PathTable, RouteMatch};
@@ -279,12 +279,6 @@ impl<'a, Data> Resource<'a, Data> {
         self.method(http::Method::GET, ep)
     }
 
-    pub fn get_with<T, S, U>(&mut self, ep: T, seed: S) -> &mut EndpointData<Data>
-        where Seeded<T, S>: Endpoint<Data, U>
-    {
-        self.method(http::Method::GET, Seeded(ep, seed))
-    }
-
     /// Add an endpoint for `HEAD` requests
     pub fn head<T: Endpoint<Data, U>, U>(&mut self, ep: T) -> &mut EndpointData<Data> {
         self.method(http::Method::HEAD, ep)