Unable create users for authentication using Postgres in emqx

Hello,

I'm using postgres as authenicator and authorization in emqx (**V5.3**). When I tried to **add a user** by using below curl command, it was giving me bad request. For your reference, I'm attaching the request and response

**Request:**

```
curl --location 'http://localhost:18083/api/v5/authentication/password_based:postgresql/users' \
--header 'accept: application/json' \
--header 'Content-Type: application/json' \
--header 'Authorization: Basic ' \
--data '{
"password": "12345678",
"user_id": "user4"
}'
```

**Response:**
code: 400
```
{
"code": "BAD_REQUEST",
"message": "User error: unsupported_operation"
}
```

FYI,
1. I have tried by inserting the values into db into their respective table. It is working as intended.
2. I have used above curl command by changing the authenicator id to in-built-database. It also worked for me.

But with postgresql I'm getting the above error

If anyone is aware of this issue, please help me out

Thanks