Update GCP auth docs

backend/src/server/routes/v1/identity-gcp-iam-auth-router.ts

@@ -6,6 +6,7 @@ import { readLimit, writeLimit } from "@app/server/config/rateLimiter";
 import { verifyAuth } from "@app/server/plugins/auth/verify-auth";
 import { AuthMode } from "@app/services/auth/auth-type";
 import { TIdentityTrustedIp } from "@app/services/identity/identity-types";
+import { validateGcpIamAuthField } from "@app/services/identity-gcp-iam-auth/identity-gcp-iam-auth-validators";
 
 export const registerIdentityGcpIamAuthRouter = async (server: FastifyZodProvider) => {
   server.route({
@@ -73,8 +74,8 @@ export const registerIdentityGcpIamAuthRouter = async (server: FastifyZodProvide
         identityId: z.string().trim()
       }),
       body: z.object({
-        allowedServiceAccounts: z.string(), // TODO: better validation
-        allowedProjects: z.string(), // TODO: better validation
+        allowedServiceAccounts: validateGcpIamAuthField,
+        allowedProjects: validateGcpIamAuthField,
         accessTokenTrustedIps: z
           .object({
             ipAddress: z.string().trim()

backend/src/services/identity-gcp-iam-auth/identity-gcp-iam-auth-validators.ts

@@ -0,0 +1,14 @@
+import { z } from "zod";
+
+export const validateGcpIamAuthField = z
+  .string()
+  .trim()
+  .default("")
+  .transform((data) => {
+    if (data === "") return "";
+    // Trim each ID and join with ', ' to ensure formatting
+    return data
+      .split(",")
+      .map((id) => id.trim())
+      .join(", ");
+  });