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/context.ts

@@ -0,0 +1,33 @@
+import {Config} from './config.js'
+import Database from './db/index.js'
+
+export type AppContextOptions = {
+  cfg: Config
+  db: Database
+}
+
+export class AppContext {
+  cfg: Config
+  db: Database
+  abortController = new AbortController()
+
+  constructor(private opts: AppContextOptions) {
+    this.cfg = this.opts.cfg
+    this.db = this.opts.db
+  }
+
+  static async fromConfig(cfg: Config, overrides?: Partial<AppContextOptions>) {
+    const db = Database.postgres({
+      url: cfg.db.url,
+      schema: cfg.db.schema,
+      poolSize: cfg.db.pool.size,
+      poolMaxUses: cfg.db.pool.maxUses,
+      poolIdleTimeoutMs: cfg.db.pool.idleTimeoutMs,
+    })
+    return new AppContext({
+      cfg,
+      db,
+      ...overrides,
+    })
+  }
+}