feat: add administrator guard

backend/prisma/schema.prisma

@@ -14,6 +14,7 @@ model User {
 
   email           String  @unique
   password        String
+  isAdministrator Boolean @default(false)
   firstName       String?
   lastName        String?
 

backend/src/auth/guard/isAdmin.guard.ts

@@ -0,0 +1,10 @@
+import { CanActivate, ExecutionContext, Injectable } from "@nestjs/common";
+import { User } from "@prisma/client";
+
+@Injectable()
+export class AdministratorGuard implements CanActivate {
+  canActivate(context: ExecutionContext): boolean {
+    const { user }: { user: User } = context.switchToHttp().getRequest();
+    return user.isAdministrator;
+  }
+}