Misleading error message when trying to change password for non-native user

[abseht]

Elasticsearch Version

8.15.2

Installed Plugins

No response

Java Version

bundled

OS Version

managed elastic.co deployment

Problem Description

Cannot change password for elastic user using these instructions

It returns

{
  "error": {
    "root_cause": [
      {
        "type": "validation_exception",
        "reason": "Validation Failed: 1: user must exist in order to change password;"
      }
    ],
    "type": "validation_exception",
    "reason": "Validation Failed: 1: user must exist in order to change password;"
  },
  "status": 400
}

Moreover, trying to do so with Terraform provider and this resource also returns below error.

│ Error: System user "elastic" not found
│ 
│   with module.password.elasticstack_elasticsearch_security_system_user.this["elastic"],
│   on ../module_elasticsearch_user/built_in_user.tf line 1, in resource "elasticstack_elasticsearch_security_system_user" "this":
│    1: resource "elasticstack_elasticsearch_security_system_user" "this" {

Steps to Reproduce

1. Go to your elastic.co console.
2. Select a deployment
3. Go to API console
4. Send request to POST /_security/user/_password with body { "password": "new-Password-12345"}
   
   OR
5. Send request to POST /_security/user/elastic/_password with the same body
   

Logs (if relevant)

No response

[elasticsearchmachine]

Pinging @elastic/es-security (Team:Security)

[tvernum]

It is intentional that you cannot change the elastic password from within Elasticsearch and Kibana on cloud.
You need to reset the password using the cloud console.

The error message is misleading (the user does exist, but cannot be managed through this API) and it would be good to clean that up.

[ankit--sethi]

Duplicates #29882