fix: make oauth2 tokens optional in smtp_imap provider schema

src/services/OAuth2TokenRefreshService.ts

@@ -114,7 +114,7 @@ export class OAuth2TokenRefreshService {
     const { oauth2 } = config;
     const now = Date.now();
 
-    if (oauth2.accessTokenExpiry - now > EXPIRY_BUFFER_MS) {
+    if (!oauth2.accessTokenExpiry || !oauth2.refreshToken || oauth2.accessTokenExpiry - now > EXPIRY_BUFFER_MS) {
       return;
     }
 

src/services/providers/channel/SmtpImapChannelProvider.ts

@@ -32,9 +32,9 @@ const oauth2ConfigSchema = z.strictObject({
   tokenUrl: z.string().url().describe('OAuth2 token endpoint URL (e.g. https://oauth2.googleapis.com/token for Gmail)'),
   clientId: z.string().describe('OAuth2 client ID'),
   clientSecret: z.string().describe('OAuth2 client secret'),
-  refreshToken: z.string().describe('OAuth2 refresh token (long-lived)'),
-  accessToken: z.string().describe('Current OAuth2 access token (rotated by the refresh service)'),
-  accessTokenExpiry: z.number().int().describe('Unix timestamp in milliseconds when the access token expires'),
+  refreshToken: z.string().optional().describe('OAuth2 refresh token (long-lived, managed by the OAuth2 callback/refresh service)'),
+  accessToken: z.string().optional().describe('Current OAuth2 access token (managed by the OAuth2 callback/refresh service)'),
+  accessTokenExpiry: z.number().int().optional().describe('Unix timestamp in milliseconds when the access token expires (managed by the OAuth2 callback/refresh service)'),
   scope: z.string().describe('OAuth2 scope string (e.g. https://www.googleapis.com/auth/gmail.modify for Gmail)'),
 }).openapi('SmtpImapOauth2Config');