feat: new background work process

This removes all previous dependencies on RabbitMQ and the need to run separate cron and requeueing processes.

spec/app/models/worker_role_spec.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+
+RSpec.describe WorkerRole do
+  let(:locker_name) { "test" }
+
+  before do
+    allow(Postal).to receive(:locker_name).and_return(locker_name)
+  end
+
+  describe ".acquire" do
+    context "when there are no existing roles" do
+      it "returns :created" do
+        expect(WorkerRole.acquire("test")).to eq(:created)
+      end
+    end
+
+    context "when the current process holds a lock for a role" do
+      it "returns :renewed" do
+        create(:worker_role, role: "test", worker: "test", acquired_at: 1.minute.ago)
+        expect(WorkerRole.acquire("test")).to eq(:renewed)
+      end
+    end
+
+    context "when the role has become stale" do
+      it "returns :stolen" do
+        create(:worker_role, role: "test", worker: "another", acquired_at: 10.minute.ago)
+        expect(WorkerRole.acquire("test")).to eq(:stolen)
+      end
+    end
+
+    context "when the role is already locked by another worker" do
+      it "returns false" do
+        create(:worker_role, role: "test", worker: "another", acquired_at: 1.minute.ago)
+        expect(WorkerRole.acquire("test")).to eq(false)
+      end
+    end
+  end
+
+  describe ".release" do
+    context "when the role is locked by the current worker" do
+      it "deletes the role and returns true" do
+        role = create(:worker_role, role: "test", worker: "test")
+        expect(WorkerRole.release("test")).to eq(true)
+        expect(WorkerRole.find_by(id: role.id)).to be_nil
+      end
+    end
+
+    context "when the role is locked by another worker" do
+      it "does not delete the role and returns false" do
+        role = create(:worker_role, role: "test", worker: "another")
+        expect(WorkerRole.release("test")).to eq(false)
+        expect(WorkerRole.find_by(id: role.id)).to be_present
+      end
+    end
+  end
+end