Improve catching of errors when loading routes

- Handle ResponseParseErros, ResponseErrors and normal errors
  differently.
- Show them all in the same `LoadError` view
- Add a subtitle to give users some more information on what could have
  gone wrong.
- Add more properties to the copyable error message to make debugging
  easier.

src/views/projects/error.ts

@@ -0,0 +1,59 @@
+import type { ErrorRoute, NotFoundRoute } from "@app/lib/router/definitions";
+import type { ProjectRoute } from "@app/views/projects/router";
+
+import { baseUrlToUrl } from "@app/lib/utils";
+import { ResponseParseError, ResponseError } from "@httpd-client/lib/fetcher";
+
+export function handleError(
+  error: Error | ResponseParseError | ResponseError,
+  route: ProjectRoute,
+): NotFoundRoute | ErrorRoute {
+  const url = baseUrlToUrl(route.node);
+  if (error instanceof ResponseError && error.status === 404) {
+    let subject;
+
+    if (route.resource === "project.commit") {
+      subject = "Commit";
+    } else if (route.resource === "project.issue") {
+      subject = "Issue";
+    } else if (route.resource === "project.patch") {
+      subject = "Patch";
+    } else {
+      subject = "Project";
+    }
+
+    return {
+      resource: "notFound",
+      params: { title: `${subject} not found` },
+    };
+  } else if (error instanceof ResponseError) {
+    return {
+      resource: "error",
+      params: {
+        error,
+        title: "Could not load this project",
+        description: `Make sure you are able to connect to the seed <a href="${url}">${url}</a>.`,
+      },
+    };
+  } else if (error instanceof ResponseParseError) {
+    return {
+      resource: "error",
+      params: {
+        error,
+        title: "Could not parse the request",
+        description:
+          "The response received from the seed does not match the expected schema, this is usually due to a version mismatch between the seed and the web interface.",
+      },
+    };
+  } else {
+    return {
+      resource: "error",
+      params: {
+        error,
+        title: "Could not load this project",
+        description:
+          "You stumbled on an unknown error, we aren't exactly sure what happened.",
+      },
+    };
+  }
+}