fix: fallback to provider ID for email when user email is missing during authentication

src/auth.ts

@@ -136,7 +136,7 @@ export const { handlers, signIn, signOut, auth } = NextAuth({
               body: JSON.stringify({
                 provider: account.provider,
                 providerId: account.providerAccountId,
-                email: user.email,
+                email: user.email || `${account.providerAccountId}@x.com`,
                 name: user.name,
                 avatar: user.image,
                 role,