feat: improved saml error messages

backend/src/@types/fastify.d.ts

@@ -136,7 +136,7 @@ declare module "fastify" {
     rateLimits: RateLimitConfiguration;
     // passport data
     passportUser: {
-      isUserCompleted: string;
+      isUserCompleted: boolean;
       providerAuthToken: string;
     };
     kmipUser: {

backend/src/ee/routes/v1/saml-router.ts

@@ -223,12 +223,18 @@ export const registerSamlRouter = async (server: FastifyZodProvider) => {
         samlConfigId: z.string().trim()
       })
     },
-    preValidation: passport.authenticate("saml", {
+    preValidation: passport.authenticate(
-      session: false,
+      "saml",
-      failureFlash: true,
+      {
-      failureRedirect: "/login/provider/error"
+        session: false
-      // this is due to zod type difference
+      },
-    }) as any,
+      async (req, res, err, user) => {
+        if (err) {
+          throw new BadRequestError({ message: `Saml authentication failed. ${err?.message}`, error: err });
+        }
+        req.passportUser = user as { isUserCompleted: boolean; providerAuthToken: string };
+      }
+    ) as any, // this is due to zod type difference
     handler: (req, res) => {
       if (req.passportUser.isUserCompleted) {
         return res.redirect(