Rename zed-server to collab

Over time, I think we may end up having multiple services, so it seems like a good opportunity to name this one more specifically while the cost is low. It just seems like naming it "zed" and "zed-server" leaves it a bit open ended.

crates/collab/src/errors.rs

@@ -0,0 +1,73 @@
+use crate::{AppState, LayoutData, Request, RequestExt};
+use async_trait::async_trait;
+use serde::Serialize;
+use std::sync::Arc;
+use tide::http::mime;
+
+pub struct Middleware;
+
+#[async_trait]
+impl tide::Middleware<Arc<AppState>> for Middleware {
+    async fn handle(
+        &self,
+        mut request: Request,
+        next: tide::Next<'_, Arc<AppState>>,
+    ) -> tide::Result {
+        let app = request.state().clone();
+        let layout_data = request.layout_data().await?;
+
+        let mut response = next.run(request).await;
+
+        #[derive(Serialize)]
+        struct ErrorData {
+            #[serde(flatten)]
+            layout: Arc<LayoutData>,
+            status: u16,
+            reason: &'static str,
+        }
+
+        if !response.status().is_success() {
+            response.set_body(app.render_template(
+                "error.hbs",
+                &ErrorData {
+                    layout: layout_data,
+                    status: response.status().into(),
+                    reason: response.status().canonical_reason(),
+                },
+            )?);
+            response.set_content_type(mime::HTML);
+        }
+
+        Ok(response)
+    }
+}
+
+// Allow tide Results to accept context like other Results do when
+// using anyhow.
+pub trait TideResultExt {
+    fn context<C>(self, cx: C) -> Self
+    where
+        C: std::fmt::Display + Send + Sync + 'static;
+
+    fn with_context<C, F>(self, f: F) -> Self
+    where
+        C: std::fmt::Display + Send + Sync + 'static,
+        F: FnOnce() -> C;
+}
+
+impl<T> TideResultExt for tide::Result<T> {
+    fn context<C>(self, cx: C) -> Self
+    where
+        C: std::fmt::Display + Send + Sync + 'static,
+    {
+        self.map_err(|e| tide::Error::new(e.status(), e.into_inner().context(cx)))
+    }
+
+    fn with_context<C, F>(self, f: F) -> Self
+    where
+        C: std::fmt::Display + Send + Sync + 'static,
+        F: FnOnce() -> C,
+    {
+        self.map_err(|e| tide::Error::new(e.status(), e.into_inner().context(f())))
+    }
+}