Bsky link card service (#4547)

* setup bskycard

* quick proof of concept for png card generation

* bskycard: use jsx

* bskycard: 3x5 profile layout

* bskycard: add butterfly overlay

* bskycard: tidy

* bskycard: separate and reorganize

* bskycard: tidy

* bskycard: tidy

* bskycard: tidy

* bskycard: poc of transparent overlay and box shadow

* bskycard: reorg impl into src/ directory

* bskycard: use more standard app structure

* bskycard: setup dockerfile, fix build

* bskycard: support for x-origin-verify

* bskycard: card layout, filter images based on labels

* bskycard: tidy

* bskycard: support cluster mode

* bskycard: handle error fetching starter pack info

* bskycard: tidy

* bskycard: fix leak on failed image fetch

* bskycard: build workflow

* bskyogcard: rename from bskycard

* bskyogcard: fix some express plumbing

* bskyogcard: add cdn tags, tidy

bskyogcard/src/context.ts

@@ -0,0 +1,44 @@
+import {readFileSync} from 'node:fs'
+
+import {AtpAgent} from '@atproto/api'
+import * as path from 'path'
+import {fileURLToPath} from 'url'
+
+import {Config} from './config.js'
+
+const __DIRNAME = path.dirname(fileURLToPath(import.meta.url))
+
+export type AppContextOptions = {
+  cfg: Config
+  appviewAgent: AtpAgent
+  fonts: {name: string; data: Buffer}[]
+}
+
+export class AppContext {
+  cfg: Config
+  appviewAgent: AtpAgent
+  fonts: {name: string; data: Buffer}[]
+  abortController = new AbortController()
+
+  constructor(private opts: AppContextOptions) {
+    this.cfg = this.opts.cfg
+    this.appviewAgent = this.opts.appviewAgent
+    this.fonts = this.opts.fonts
+  }
+
+  static async fromConfig(cfg: Config, overrides?: Partial<AppContextOptions>) {
+    const appviewAgent = new AtpAgent({service: cfg.service.appviewUrl})
+    const fonts = [
+      {
+        name: 'Inter',
+        data: readFileSync(path.join(__DIRNAME, 'assets', 'Inter-Bold.ttf')),
+      },
+    ]
+    return new AppContext({
+      cfg,
+      appviewAgent,
+      fonts,
+      ...overrides,
+    })
+  }
+}