Delphi TidHTTP web service security usernametoken - delphi

Question

I am trying to use Delphi and Indy's TIdHTTP to access a site using the security usernametoken aspect.
The SOAP request has headers for password type=urladdressforoasis password
The server's classnameproxy.config file from the vendor has this:
<basicHttpBinding>
<binding name="BasicHttpBinding_ZZ_myInt">
<security mode="TransportWithMessageCredential" />
</binding>
</basicHttpBinding>
So I am trying to add custom headers to TIdHTTP using the following code:
idHTTP.Request.CustomHeaders.AddValue('Authorization', 'Basic ' + TIdEncoderMIME.EncodeString(string(aUserID) + ':' + string(aPWD), IndyTextEncoding_ASCII()));
Obviously this is incorrect for some reason. I have looked around for TIdHTTP and oasis and usernametoken but found nothing. Maybe I am looking for the wrong keywords?
Is it possible to use TIdHTTP to access web services using a security usernametoken?
function Post_XML(aURL, aUserID, aPWD, aInputFile, aOutputFile, aContentType, aCharset, aShow: pAnsiChar):integer; stdcall;
var
sRequest,
sResponse : TFileStream;
idHTTP : TidHTTP;
SSLHandler : TidSSLIOHandlerSocketOpenSSL;
EnvVar : string;
begin
Result := 0;
begin
try
begin
sRequest := TFileStream.Create(string(aInputFile), fmOpenRead or fmShareDenyWrite);
sResponse := TFileStream.Create(string(aOutputFile), fmCreate or fmShareDenyRead or fmOpenWrite);
end;
except on E: Exception do
begin
Result := 99;
end;
end;
try
begin
EnvVar := '';
EnvVar := System.SysUtils.GetEnvironmentVariable('use_a_proxy');
SSLHandler := TIdSSLIOHandlerSocketOpenSSL.Create;
SSLHandler.SSLOptions.SSLVersions := [sslvSSLv23, sslvSSLv3, sslvTLSv1, sslvTLSv1_1, sslvTLSv1_2];
SSLHandler.SSLOptions.Mode := sslmUnassigned;
idHTTP := TidHTTP.Create;
idHTTP.ConnectTimeout := 60000;
idHTTP.ReadTimeout := 60000;
idHTTP.HandleRedirects := True;
idHTTP.IOHandler := SSLHandler;
if UpperCase(EnvVar) = 'ON' then
begin
idHTTP.ProxyParams.ProxyServer := '127.0.0.1';
idHTTP.ProxyParams.ProxyPort := 8888;
end;
idHTTP.Request.ContentType := string(aContentType);
idHTTP.Request.CharSet := string(aCharSet);
idhttp.Request.CustomHeaders.AddValue('SOAPAction', 'http://bustax.tntax.tn.gov/BusTaxRequest');
if aUserid <> '' then
begin
idHTTP.Request.BasicAuthentication := True;
idhttp.Request.Username := aUserid;
idHTTP.Request.Password := aPwd;
end;
idHTTP.Post(trim(string(aURL)), sRequest, sResponse);
FreeAndNil(SSLHandler);
FreeAndNil(idHTTP);
end;
except
on E: EIdHTTPProtocolException do
begin
ShowMessage(AnsiString('Protocol Error: ' + E.Message));
Result := E.ErrorCode;
end;
on E: EIdSocketError do
begin
ShowMessage(AnsiString('Socket Error: ' + E.Message));
Result := E.LastError;
end;
on E: EIdException do
begin
ShowMessage(AnsiString('HTTP Error: ' + E.Message));
Result := HTTPMain.ResponseCode;
end;
on E: Exception do
begin
ShowMessage(AnsiString('Error: ' + E.Message));
Result := HTTPMain.ResponseCode;
end;
end;
FreeAndNil(sRequest);
FreeAndNil(sResponse);
end;
end;
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:oas="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" xmlns:bus="http://bustax.tntax.tn.gov">
<soapenv:Header>
<oas:Security>
<oas:UsernameToken>
<oas:Username>myUsername</oas:Username>
<oas:Password Type="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-username-token-profile-1.0#PasswordText">myPassword</oas:Password>
</oas:UsernameToken>
</oas:Security>
</soapenv:Header>
<soapenv:Body>
<bus:BusTaxRequest>
<bus:JurisdictionSITUS>1900</bus:JurisdictionSITUS>
<bus:TransactionId>123456</bus:TransactionId>
</bus:BusTaxRequest>
</soapenv:Body>
</soapenv:Envelope>