Add stimulus controller to handle ToS banner

Plus spec

spec/javascripts/stimulus/terms_of_service_banner_controller_test.js

@@ -0,0 +1,64 @@
+/**
+ * @jest-environment jsdom
+ */
+
+import { Application } from "stimulus"
+import terms_of_service_banner_controller from "../../../app/webpacker/controllers/terms_of_service_banner_controller"
+
+describe("TermsOfServiceBannerController", () => {
+  beforeAll(() => {
+    const application = Application.start()
+    application.register("terms-of-service-banner", terms_of_service_banner_controller)
+  })
+
+  beforeEach(() => {
+    document.body.innerHTML = `
+      <meta content="abc123authenticitytoken" name="csrf-token">
+      <div 
+        id="test-controller-div" 
+        data-controller="terms-of-service-banner" 
+        data-terms-of-service-banner-url-value="admin/users/10/accept_terms_of_service"
+      >
+        <div>
+          <span>Terms of service has been updated </span> 
+          <button id="test-accept-banner" data-action="click->terms-of-service-banner#accept">
+            Accept terms of service
+          </button>
+          <button id="test-close-banner" data-action="click->terms-of-service-banner#close_banner">close</button>
+        </div>
+      </div>
+    `
+  })
+
+  describe("#close", () => {
+    it("removes the banner", () => {
+      const closeButton = document.getElementById("test-close-banner")
+      closeButton.click()
+      
+      expect(document.getElementById("test-controller-div")).toBeNull()
+    })
+  })
+
+  describe("#accept", () => {
+    it("fires a request to accept terms of service", () => {
+      const mockFetch = jest.fn().mockImplementation( (_url, _options) =>
+        Promise.resolve({
+          ok: true,
+          json: () => "",
+        })
+      )
+      window.fetch = (_url, _options) => {
+        return mockFetch(_url, _options)
+      }
+
+      const button = document.getElementById("test-accept-banner")
+
+      button.click()
+     
+      expect(mockFetch).toHaveBeenCalledWith(
+        "admin/users/10/accept_terms_of_service",
+        { headers: { "X-CSRF-Token": "abc123authenticitytoken" }, method: "post" }
+      )
+    })
+  })
+})