Added usage check to delete endpoints

app/Models/User.php

@@ -149,6 +149,14 @@ class User extends Authenticatable implements FilamentUser, MustVerifyEmail
         return $this->hasMany(TimeEntry::class);
     }
 
+    /**
+     * @return HasMany<ProjectMember>
+     */
+    public function projectMembers(): HasMany
+    {
+        return $this->hasMany(ProjectMember::class, 'user_id');
+    }
+
     /**
      * @param  Builder<User>  $builder
      */