feat: add webhook_subscription table and CRUD endpoints

- Migration: CREATE TABLE webhook_subscription (id, did, method, url) with index on did
- db.ts: addWebhookSubscription and deleteWebhooksByDid helpers
- server.ts: POST /:did/webhooks (201) and DELETE /:did/webhooks (204)

server.ts

@@ -1,5 +1,10 @@
 import { Application, Router } from "@oak/oak";
-import { getNotes, getNotesByDid } from "./src/data/db.ts";
+import {
+  addWebhookSubscription,
+  deleteWebhooksByDid,
+  getNotes,
+  getNotesByDid,
+} from "./src/data/db.ts";
 import { log } from "./src/log.ts";
 
 const router = new Router();
@@ -23,6 +28,26 @@ router.get("/:did/notes", (ctx) => {
   ctx.response.body = getNotesByDid(did, cursor, limit);
 });
 
+router.post("/:did/webhooks", async (ctx) => {
+  const { did } = ctx.params;
+  const body = await ctx.request.body.json();
+  const { method, url } = body ?? {};
+  if (!method || !url) {
+    ctx.response.status = 400;
+    ctx.response.body = { error: "method and url are required" };
+    return;
+  }
+  const subscription = addWebhookSubscription({ did, method, url });
+  ctx.response.status = 201;
+  ctx.response.body = subscription;
+});
+
+router.delete("/:did/webhooks", (ctx) => {
+  const { did } = ctx.params;
+  deleteWebhooksByDid(did);
+  ctx.response.status = 204;
+});
+
 // router.delete("/:did/:rkey", async (ctx) => {
 //   const { did, rkey } = ctx.params;
 //   let verifiedDid: string;