fix: 🐛 OIDC authentications not properly showing username (#2930)

* fix: 🐛 properly show username for oidc auth method in user menu

* test: 💍 fix admin ui tests

* test: 💍 fix desktop ui tests

* refactor: 💡 admin to not store username in authenticated object

* refactor: 💡 use getter in app controller

* test: 💍 POC for how we could update our tests to use auth account

* refactor: 💡 remove unused service

* test: 💍 fix all tests in ui/admin

* test: 💍 revert one change

* refactor: 💡 update ui/desktop w/ feedback + fix tests

* refactor: 💡 add in error handling

* refactor: 💡 cleanup unused service

* test: 💍 fix e2e test selector

✅ Closes: https://hashicorp.atlassian.net/browse/ICU-17231

e2e-tests/admin/tests/auth-method-oidc-vault.spec.js

@@ -133,9 +133,7 @@ test(
       ).toBeVisible();
 
       // Log back in as an admin
-      await page.getByRole('button', { name: 'User Menu' }).click();
-      await page.getByRole('button', { name: 'Sign Out' }).click();
-      await expect(page.getByRole('button', { name: 'Sign In' })).toBeVisible();
+      await loginPage.logout(email);
       await loginPage.login(adminLoginName, adminPassword);
       await expect(
         page.getByRole('navigation', { name: 'breadcrumbs' }).getByText('Orgs'),