test: Mock bull, fix setInterval capturing memory in tests

Towards #3939

server/__mocks__/bull.ts

@@ -0,0 +1,43 @@
+export default class Queue {
+  done() {
+    //
+  }
+
+  on() {
+    //
+  }
+
+  count() {
+    return 0;
+  }
+
+  getDelayedCount() {
+    return 0;
+  }
+
+  add = function (data: any) {
+    const job = this.createJob(data);
+
+    if (!this.handler) {
+      throw Error(
+        "Mocking version requires handler to be set before first add()"
+      );
+    }
+
+    this.handler(job, this.done);
+  };
+
+  process = function (handler: any) {
+    if (this.handler) {
+      throw Error("Cannot define a handler more than once per Queue instance");
+    }
+
+    this.handler = handler;
+  };
+
+  createJob = function (data: any) {
+    return {
+      data: data,
+    };
+  };
+}