Error authenticating in the Orchestrator using the old authentication method

Hi.

We are having problems with some of our clients trying to authenticate in some accounts in the public orchestrator.

They are using some old accounts, that allow them to authenticate using the old authentication method, sending the tenant name, username and password parameters. This method worked fine until last week.
The body is like this:

{
    "tenancyName": "{{tenancyName}}",
    "usernameOrEmailAddress": "{{usernameOrEmailAddress}}",
    "password": "{{password}}"
}

The first symptom of the problem was this error:

{
    "type": "https://tools.ietf.org/html/rfc7231#section-6.5.13",
    "title": "Unsupported Media Type",
    "status": 415,
    "traceId": "00-04149b08872e6641a838523716fb22ca-8ba755697d40a94a-00"
}

Then we explicitly sent the header in the http request set to UTF-8 and works again. However, We noticed that this authentication service ( {{url}}/api/Account/Authenticate ) is working in an intermittent way, the most of times is returning this error.

{"message":"An error has occurred.","errorCode":0,"resourceIds":null}

We have two questions:

  1. This kind of authentication will be deprecated definitely for these old accounts soon?
  2. What have changed recently in this authentication service, and why is mandatory to send the UTF-8 header in the request?

Thank you.

Manuel