test(oauth-provider): adapt merged token/private-key-jwt tests to next's APIs (#9533)

These test files auto-merged main's additions onto next's refactored test
surface, producing runtime failures tsc could not catch:

- token.test.ts called main's sync createRefreshAccessTokenRequest, which next
  renamed to the async refreshAccessTokenRequest; the calls now await it and
  the concurrent-rotation helper is async.
- private-key-jwt-e2e.test.ts hit the merged-in #9578 gate: both the provider
  and RP test instances create the same default user, so the OAuth sign-in
  links to the RP's unverified local user and is blocked. The RP sets
  requireLocalEmailVerified: false so the test exercises private_key_jwt
  rather than the (separately covered) email-verification gate.
- utils/basic-auth.test.ts is removed: next made basicToClientCredentials
  private, and its colon-preservation coverage now lives in core's
  basic-credentials.test.ts.

Full oauth-provider suite green (24 files, 378 tests).

packages/oauth-provider/src/private-key-jwt-e2e.test.ts

@@ -124,6 +124,7 @@ describe("private_key_jwt e2e", async () => {
 			account: {
 				accountLinking: {
 					trustedProviders: [providerId],
+					requireLocalEmailVerified: false,
 				},
 			},
 			plugins: [
@@ -265,6 +266,7 @@ describe("private_key_jwt e2e", async () => {
 			account: {
 				accountLinking: {
 					trustedProviders: [providerId],
+					requireLocalEmailVerified: false,
 				},
 			},
 			plugins: [

packages/oauth-provider/src/token.test.ts

@@ -1044,7 +1044,7 @@ describe("oauth token - refresh_token", async () => {
 		expect(tokens?.refresh_token).toBeDefined();
 
 		async function refresh(refreshToken: string) {
-			const { body, headers } = createRefreshAccessTokenRequest({
+			const { body, headers } = await refreshAccessTokenRequest({
 				refreshToken,
 				options: {
 					clientId: oauthClient!.client_id,
@@ -1102,7 +1102,7 @@ describe("oauth token - refresh_token", async () => {
 		expect(tokens?.refresh_token).toBeDefined();
 
 		async function refresh(refreshToken: string) {
-			const { body, headers } = createRefreshAccessTokenRequest({
+			const { body, headers } = await refreshAccessTokenRequest({
 				refreshToken,
 				options: {
 					clientId: oauthClient!.client_id,
@@ -1180,7 +1180,7 @@ describe("oauth token - refresh_token", async () => {
 		// Reusing the revoked refresh token must trip the family-invalidation
 		// guard in handleRefreshTokenGrant (revoked flag → invalidate family).
 		const { body: replayBody, headers: replayHeaders } =
-			createRefreshAccessTokenRequest({
+			await refreshAccessTokenRequest({
 				refreshToken: tokens!.refresh_token!,
 				options: {
 					clientId: oauthClient.client_id,
@@ -1218,8 +1218,8 @@ describe("oauth token - refresh_token", async () => {
 		expect(tokens?.refresh_token).toBeDefined();
 		const parentToken = tokens!.refresh_token!;
 
-		const refresh = () => {
-			const { body, headers } = createRefreshAccessTokenRequest({
+		const refresh = async () => {
+			const { body, headers } = await refreshAccessTokenRequest({
 				refreshToken: parentToken,
 				options: {
 					clientId: oauthClient!.client_id,

packages/oauth-provider/src/utils/basic-auth.test.ts

@@ -1,39 +0,0 @@
-import { base64 } from "@better-auth/utils/base64";
-import { describe, expect, it } from "vitest";
-
-import { basicToClientCredentials } from "./index";
-
-function encodeBasic(clientId: string, clientSecret: string) {
-	const raw = `${clientId}:${clientSecret}`;
-	const encoded = base64.encode(new TextEncoder().encode(raw));
-	return `Basic ${encoded}`;
-}
-
-/**
- * @see https://datatracker.ietf.org/doc/html/rfc7617#section-2
- */
-describe("basicToClientCredentials", () => {
-	it("preserves colons inside client_secret per RFC 7617", () => {
-		const clientId = "cid";
-		const clientSecret = "pa:ss:word";
-
-		const result = basicToClientCredentials(
-			encodeBasic(clientId, clientSecret),
-		);
-
-		expect(result).toBeDefined();
-		expect(result?.client_id).toBe(clientId);
-		expect(result?.client_secret).toBe(clientSecret);
-	});
-
-	it("keeps a trailing colon as part of client_secret", () => {
-		const clientId = "cid";
-		const clientSecret = "secret:";
-
-		const result = basicToClientCredentials(
-			encodeBasic(clientId, clientSecret),
-		);
-
-		expect(result?.client_secret).toBe(clientSecret);
-	});
-});