Bsky short link service (#4542)

* bskylink: scaffold service w/ initial config and schema

* bskylink: implement link creation and redirects

* bskylink: tidy

* bskylink: tests

* bskylink: tidy, add error handler

* bskylink: add dockerfile

* bskylink: add build

* bskylink: fix some express plumbing

* bskyweb: proxy fallthrough routes to link service redirects

* bskyweb: build w/ link proxy

* Add AASA to bskylink (#4588)

---------

Co-authored-by: Hailey <me@haileyok.com>

bskylink/src/routes/health.ts

@@ -0,0 +1,20 @@
+import {Express} from 'express'
+import {sql} from 'kysely'
+
+import {AppContext} from '../context.js'
+import {handler} from './util.js'
+
+export default function (ctx: AppContext, app: Express) {
+  return app.get(
+    '/_health',
+    handler(async (_req, res) => {
+      const {version} = ctx.cfg.service
+      try {
+        await sql`select 1`.execute(ctx.db.db)
+        return res.send({version})
+      } catch (err) {
+        return res.status(503).send({version, error: 'Service Unavailable'})
+      }
+    }),
+  )
+}