feat(bun): Support new Bun.serve APIs

[AbhiPrasad]

Supercedes #15978

resolves #15941
resolves #15827
resolves #15816

Bun recently updated their Bun.serve API with new functionality, which unfortunately broke our existing instrumentation. This is detailed with https://bun.sh/docs/api/http#bun-serve. Specifically, they added a new routing API that looks like so:

Bun.serve({
  // `routes` requires Bun v1.2.3+
  routes: {
    // Dynamic routes
    "/users/:id": req => {
      return new Response(`Hello User ${req.params.id}!`);
    },

    // Per-HTTP method handlers
    "/api/posts": {
      GET: () => new Response("List posts"),
      POST: async req => {
        const body = await req.json();
        return Response.json({ created: true, ...body });
      },
    },

    // Wildcard route for all routes that start with "/api/" and aren't otherwise matched
    "/api/*": Response.json({ message: "Not found" }, { status: 404 }),

    // Redirect from /blog/hello to /blog/hello/world
    "/blog/hello": Response.redirect("/blog/hello/world"),

    // Serve a file by buffering it in memory
    "/favicon.ico": new Response(await Bun.file("./favicon.ico").bytes(), {
      headers: {
        "Content-Type": "image/x-icon",
      },
    }),
  },

  // (optional) fallback for unmatched routes:
  // Required if Bun's version < 1.2.3
  fetch(req) {
    return new Response("Not Found", { status: 404 });
  },
});

Because there are now dynamic routes and wildcard routes, we can actually generate route transaction source and send parameterized routes to Sentry. The fetch API is still supported.

The only API we don't support is static routes/responses. This is because these are optimized by Bun itself, and if we turn it into a function (which we need to do to time it), we'll lose out on the optimization. For now they aren't instrumented.

[Lms24]

Nice!

[Lms24]

l: IIUC correctly, we likely won't ever instrument static routes to avoid breaking the customization? So is this TODO even necessary?

Suggested change

// TODO: Handle static routes

[AbhiPrasad]

I shot a message to the Bun team about this, I guess we can remove the TODO in the code, and instead create a new GH issue we can use to track it.

If the bun team comes back with it not being possible, we can just close the issue and change the docs accordingly.