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'

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

* Iterate

* Iterate

* Fix test

---------

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apps/web/test/test-utils/auth.ts

@@ -6,4 +6,4 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-export { makeDelegatedAuthConfig, mockOpenIdConfiguration } from "matrix-js-sdk/src/testing";
+export { makeDelegatedAuthMetadata } from "matrix-js-sdk/src/testing";

apps/web/test/test-utils/test-utils.ts

@@ -27,7 +27,7 @@ import {
     type IPushRules,
     RelationType,
     JoinRule,
-    type OidcClientConfig,
+    type ValidatedAuthMetadata,
     type GroupCall,
     type EventStatus,
     type ICreateRoomOpts,
@@ -778,7 +778,7 @@ export function mkRoomState(
 export function mkServerConfig(
     hsUrl: string,
     isUrl: string,
-    delegatedAuthentication?: OidcClientConfig,
+    delegatedAuthentication?: ValidatedAuthMetadata,
 ): ValidatedServerConfig {
     return {
         hsUrl,