Add vue component for confirmation popover

Have the confirmation popover in a separate Vue component fixes a bug in
IE that was causing the `form` element in the popover to be ignored.

Since `form`s cannot be nested, the `form` element in the popover was
being discarded by IE and the revoke/resend invitation buttons did
nothing.

Breaking the functionality into a Vue component moves the `form` into a
separate template. When the popover is displayed, the component is added
to the DOM at the end, so the `form` is properly not-nested.

js/components/__tests__/__snapshots__/confirmation_popover.test.js.snap

@@ -0,0 +1,3 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`ConfirmationPopover matches snapshot 1`] = `<v-popover placement="top-start"><template></template> <button type="button" class="tooltip-target">Do something dangerous</button></v-popover>`;

js/components/__tests__/confirmation_popover.test.js

@@ -0,0 +1,22 @@
+import { shallowMount } from '@vue/test-utils'
+
+import ConfirmationPopover from '../confirmation_popover'
+
+
+describe('ConfirmationPopover', () => {
+  it('matches snapshot', () => {
+    const wrapper = shallowMount(ConfirmationPopover, {
+      propsData: {
+        action: '/some-url',
+        btn_text: 'Do something dangerous',
+        cancel_btn_text: 'Cancel',
+        confirm_btn_text: 'Confirm',
+        confirm_msg: 'Are you sure you want to do that?',
+        csrf_token: '42'
+      }
+    })
+
+    expect(wrapper).toMatchSnapshot()
+  })
+})
+