To change the pasword.

Request

{
      "$schema": "http://json-schema.org/draft-07/schema#",
      "title": "passwd - request",
      "type": "object",
      "properties": {
        "oldPassword": {
          "type": "string"
        },
        "password": {
          "type": "string"
        }
      },
      "required": [
        "oldPassword",
        "password"
      ],
      "additionalProperties": false
}

Meaning of json items: 

{
      "oldPassword": "1!54.ee44",
      "password": "new44.55ewn"
}

Response