How to translate CURL command to Delphi - rest

Question

I'm trying to use Delphi 10.2 TREST components with AWS. I have a CURL command that works:
curl -X POST --data #GetIDData.json -H "X-Amz-Target: AWSCognitoIdentityService.GetId" -H "Content-Type: application/x-amz-json-1.1" https://cognito-identity.us-east-1.amazonaws.com/
GetIDData.json contains this:
{"IdentityPoolId":"us-east-1:XXXXXXXXXXXXXXXXXXXXX"}
Successful result is this:
{"IdentityId":"us-east-1:XXXXXXXXXXXXXXXXXXXXX"}
I'd like to duplicate that result using Delphi TREST components:
...
fClient := TRESTClient.Create('https://cognito-identity.us-east-1.amazonaws.com/');
fClient.SetHTTPHeader('Content-Type', 'application/x-amz-json-1.1');
fClient.SetHTTPHeader('X-Amz-Target', 'AWSCognitoIdentityService.GetId');
fRequest := TRESTRequest.Create(nil);
fRequest.Client := fClient;
fRequest.Method := TRESTRequestMethod.rmPOST;
// fRequest.AddBody('{"IdentityPoolId":"us-east-1:XXXXXXXXXXXXXXXXXXXXX"}', ctAPPLICATION_JSON);
lJObj := TJSONObject.Create;
lJObj.AddPair('IdentityPoolId', 'us-east-1:XXXXXXXXXXXXXXXXXXXXX');
fRequest.AddBody(lJObj);
fRequest.Execute;
str := fRequest.Response.Content;
...
But the result is an error:
{"Output":"__type":"com.amazon.coral.service#UnknownOperationException","message":null},"Version":"1.0"}
Downloading OpenSSL and putting the dlls into System32 did not help.
Can anyone tell me what I'm doing wrong?

Answer 1

This works:
...
lClient := TRESTClient.Create('https://cognito-identity.us-east-1.amazonaws.com/');
lRequest := TRESTRequest.Create(nil);
lRequest.Client := lClient;
lRequest.Method := TRESTRequestMethod.rmPOST;
lParam := lRequest.Params.AddItem;
lParam.name := 'X-Amz-Target';
lParam.Value := 'AWSCognitoIdentityService.GetId';
lParam.ContentType := ctNone;
lParam.Kind := pkHTTPHEADER;
lParam := lRequest.Params.AddItem;
lParam.name := 'Content-Type';
lParam.Value := 'application/x-amz-json-1.1';
lParam.ContentType := ctNone;
lParam.Kind := pkHTTPHEADER;
lParam.Options := [poDoNotEncode];
lRequest.AddBody('{"IdentityPoolId":"us-east-1:XXXXXXXXXXXXXXXXXXXXX"}', ctAPPLICATION_JSON);
lRequest.Execute;
...
WireShark was not as helpful as I wanted because its doc is out of date and I'm using encryption. But the website mentioned by #Christophe Morio in this post made finding a solution a piece of cake.