Rest endpoint to load by projectId (#1863)

## Description

1. What is this PR about (link the issue and add a short description)
Add REST endpoint to get the latest buildId based on projectId:
`/rest/buildId/<projectId>`

Should return buildId or null (which means the project is not published
yet).

It is required for the new CLI.

## Steps for reproduction

1. click button
3. expect xyz

## Code Review

- [ ] hi @kof, I need you to do
  - conceptual review (architecture, feature-correctness)
  - detailed review (read every line)
  - test it on preview

## Before requesting a review

- [x] made a self-review
- [ ] added inline comments where things may be not obvious (the "why",
not "what")

## Before merging

- [x] tested locally and on preview environment (preview dev login:
5de6)
- [ ] updated [test
cases](https://github.com/webstudio-is/webstudio-builder/blob/main/apps/builder/docs/test-cases.md)
document
- [ ] added tests
- [ ] if any new env variables are added, added them to `.env.example`
and the `builder/env-check.js` if mandatory

apps/builder/app/routes/rest.buildId.$projectId.tsx

@@ -0,0 +1,39 @@
+import { json, type LoaderArgs } from "@remix-run/node";
+import { db as projectDb } from "@webstudio-is/project/index.server";
+import { sentryException } from "~/shared/sentry";
+import { createContext } from "~/shared/context.server";
+
+export const loader = async ({
+  params,
+  request,
+}: LoaderArgs): Promise<{ buildId: string | null }> => {
+  try {
+    const projectId = params.projectId;
+
+    if (projectId === undefined) {
+      throw json("Required project id", { status: 400 });
+    }
+
+    const context = await createContext(request);
+
+    const project = await projectDb.project.loadById(projectId, context);
+    const buildId = project.latestBuild?.buildId ?? null;
+
+    return {
+      buildId,
+    };
+  } catch (error) {
+    // If a Response is thrown, we're rethrowing it for Remix to handle.
+    // https://remix.run/docs/en/v1/api/conventions#throwing-responses-in-loaders
+    if (error instanceof Response) {
+      throw error;
+    }
+
+    sentryException({ error });
+
+    // We have no idea what happened, so we'll return a 500 error.
+    throw json(error instanceof Error ? error.message : String(error), {
+      status: 500,
+    });
+  }
+};

packages/project/src/db/project.ts

@@ -33,6 +33,10 @@ export const loadById = async (
     },
   });
 
+  if (data === null) {
+    throw new Error(`Project ${projectId} not found`);
+  }
+
   return Project.parse(data);
 };