Bugfix/improve error handling in access endpoints (#7392)

* Improve error handling

* Update changelog

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Fixed
+
+- Improved the error handling in the access endpoints (`POST` and `PUT`) to return `400 Bad Request` when granting access to a non-existent user
+
 ## 3.31.0 - 2026-07-20
 
 ### Changed

apps/api/src/app/access/access.controller.ts

@@ -87,7 +87,7 @@ export class AccessController {
     }
 
     try {
-      return this.accessService.createAccess({
+      return await this.accessService.createAccess({
         alias: data.alias || undefined,
         granteeUser: data.granteeUserId
           ? { connect: { id: data.granteeUserId } }
@@ -155,7 +155,7 @@ export class AccessController {
     }
 
     try {
-      return this.accessService.updateAccess({
+      return await this.accessService.updateAccess({
         data: {
           alias: data.alias,
           granteeUser: data.granteeUserId