chore: Move to Typescript (#2783)

This PR moves the entire project to Typescript. Due to the ~1000 ignores this will lead to a messy codebase for a while, but the churn is worth it – all of those ignore comments are places that were never type-safe previously.

closes #1282

server/emails/index.ts

@@ -0,0 +1,42 @@
+import Koa from "koa";
+import Router from "koa-router";
+import { NotFoundError } from "../errors";
+import { Mailer } from "../mailer";
+
+const emailPreviews = new Koa();
+const router = new Router();
+
+router.get("/:type/:format", async (ctx) => {
+  let mailerOutput;
+  const mailer = new Mailer();
+
+  mailer.transporter = {
+    // @ts-expect-error ts-migrate(7006) FIXME: Parameter 'data' implicitly has an 'any' type.
+    sendMail: (data) => (mailerOutput = data),
+  };
+
+  switch (ctx.params.type) {
+    // case 'emailWithProperties':
+    //   mailer.emailWithProperties('user@example.com', {...properties});
+    //   break;
+    default:
+      if (Object.getOwnPropertyNames(mailer).includes(ctx.params.type)) {
+        mailer[ctx.params.type]("user@example.com");
+      } else {
+        throw NotFoundError("Email template could not be found");
+      }
+  }
+
+  if (!mailerOutput) return;
+
+  if (ctx.params.format === "text") {
+    // @ts-expect-error ts-migrate(2339) FIXME: Property 'text' does not exist on type 'never'.
+    ctx.body = mailerOutput.text;
+  } else {
+    // @ts-expect-error ts-migrate(2339) FIXME: Property 'html' does not exist on type 'never'.
+    ctx.body = mailerOutput.html;
+  }
+});
+emailPreviews.use(router.routes());
+
+export default emailPreviews;