Adapt OAuth2 implementation to Matrix Spec v1.18 (#34026)

* Adapt OAuth2 implementation to Matrix Spec v1.18

* Handle more cases of oidc->oauth

* Fix test

* Fix read back of oauth2 context

* Iterate

* Fix tests

* Discard changes to apps/web/playwright/e2e/settings/account-user-settings-tab.spec.ts

* Fix test

* Fix test

* Fix test

* Potential fix for pull request finding 'Unused variable, import, function or class'

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* Iterate

* Iterate

* Fix test

---------

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apps/web/test/viewmodels/menus/UserMenuViewModel-test.ts

@@ -63,15 +63,12 @@ describe("UserMenuViewModel", () => {
     });
 
     it("should show a link for account management", async () => {
-        const vm = new UserMenuViewModel(
-            { ownProfileStore: mockOwnProfileStore },
-            dispatcher,
-            client,
-            true,
-            "https://example.org/",
-        );
+        client.getAuthMetadata.mockResolvedValue({ account_management_uri: "https://example.org/" } as any);
+        const vm = new UserMenuViewModel({ ownProfileStore: mockOwnProfileStore }, dispatcher, client, true);
         vm.setOpen(true);
-        expect(vm.getSnapshot().manageAccountHref).toEqual("https://example.org/");
+        await waitFor(() => {
+            expect(vm.getSnapshot().manageAccountHref).toEqual("https://example.org/");
+        });
     });
 
     it("should generate a menu options for a guest", () => {