MFA: Change GenerateSecretKey Response code from 403 to 201

[asmithakarun]

GenerateSecretKeyRequired error response should behave similar to that of PasswordChangeRequired.

[asmithakarun]

Tested By:

• Created read-only user
• Enabled MFA for all users (system-wide config)
• When readonly user logs in, GenerateSecretKeyRequired is sent back in redfish response along with session creation details, and verified that the return code is 201

Note: Unnecessary use of -X or --request, POST is already inferred.
* Host r<...>:443 was resolved.
...
* using HTTP/1.x
> POST /redfish/v1/SessionService/Sessions HTTP/1.1
> Host: rain71bmc.aus.stglabs.ibm.com
> User-Agent: curl/8.7.1
> Accept: */*
> Content-Type: application/json
> Content-Length: 51
> 
* upload completely sent off: 51 bytes
< HTTP/1.1 201 Created
< Allow: GET, HEAD, POST
...
{
  "@Message.ExtendedInfo": [
    {
      "@odata.type": "#Message.v1_1_1.Message",
      "Message": "The Time-based One-Time Password (TOTP) secret key for this account must be generated before access is granted.  Perform the GenerateSecretKey action at URI '/redfish/v1/AccountService/Accounts/readonly_test' and retain the secret key from the response.",
      "MessageArgs": [
        "/redfish/v1/AccountService/Accounts/readonly_test"
      ],
      "MessageId": "Base.1.19.GenerateSecretKeyRequired",
      "MessageSeverity": "Critical",
      "Resolution": "Generate secret key for this account by performing the `GenerateSecretKey` action on the referenced URI and retaining the secret key from the action response to produce a Time-based One-Time Password (TOTP) for the `Token` property in future session creation requests."
    }
  ],
  "@odata.id": "/redfish/v1/SessionService/Sessions/<>",
  "@odata.type": "#Session.v1_7_0.Session",
  "ClientOriginIPAddress": "9.5.7.19",
  "Description": "Manager User Session",
  "Id": "SqDPklcEVk",
  "Name": "User Session",
  "Roles": [
    "ReadOnly"
  ],
  "UserName": "readonly_test"
* Connection #0 to host rain71bmc.aus.stglabs.ibm.com left intact
}```

[asmithakarun]

Upstream: https://gerrit.openbmc.org/c/openbmc/bmcweb/+/87559