Configure mule HTTP POST to replace a curl expression return an HTTP 400

Hi,

I'm new on mule and I try to replace a curl expression with the Mule HTPP connector :

curl 'https://my-test-dns/api/login' -X POST -H 'Accept: application/json' -H 'Content-Type: application/json; charset=UTF-8' -d '{ "username" : "myuser", "password" : "mypassword"}'

in Mule I've currently configure this the connection seems ok because I receive an HTTP 400 but I expect that the Body of the http post is not correctly formated

<?xml version="1.0" encoding="UTF-8"?>
    <mule xmlns:json="http://www.mulesoft.org/schema/mule/json" xmlns:tls="http://www.mulesoft.org/schema/mule/tls" xmlns:batch="http://www.mulesoft.org/schema/mule/batch"
    	xmlns:metadata="http://www.mulesoft.org/schema/mule/metadata" xmlns:file="http://www.mulesoft.org/schema/mule/file" xmlns:dw="http://www.mulesoft.org/schema/mule/ee/dw" xmlns:http="http://www.mulesoft.org/schema/mule/http" xmlns:tracking="http://www.mulesoft.org/schema/mule/ee/tracking" xmlns="http://www.mulesoft.org/schema/mule/core" xmlns:doc="http://www.mulesoft.org/schema/mule/documentation"
    	xmlns:spring="http://www.springframework.org/schema/beans" 
    	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xsi:schemaLocation="http://www.mulesoft.org/schema/mule/batch http://www.mulesoft.org/schema/mule/batch/current/mule-batch.xsd
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-current.xsd
    http://www.mulesoft.org/schema/mule/core http://www.mulesoft.org/schema/mule/core/current/mule.xsd
    http://www.mulesoft.org/schema/mule/http http://www.mulesoft.org/schema/mule/http/current/mule-http.xsd
    http://www.mulesoft.org/schema/mule/file http://www.mulesoft.org/schema/mule/file/current/mule-file.xsd
    http://www.mulesoft.org/schema/mule/ee/dw http://www.mulesoft.org/schema/mule/ee/dw/current/dw.xsd
    http://www.mulesoft.org/schema/mule/ee/tracking http://www.mulesoft.org/schema/mule/ee/tracking/current/mule-tracking-ee.xsd
    http://www.mulesoft.org/schema/mule/tls http://www.mulesoft.org/schema/mule/tls/current/mule-tls.xsd
    http://www.mulesoft.org/schema/mule/json http://www.mulesoft.org/schema/mule/json/current/mule-json.xsd">
        <http:request-config name="HTTPSGetUnboxToken" protocol="HTTPS" host="my-test-dns" port="443" basePath="/" doc:name="HTTP Request Configuration">
            <tls:context>
                <tls:trust-store insecure="true"/>
            </tls:context>
        </http:request-config>
        <flow name="cafetariaplanFlow">
            <file:inbound-endpoint path="C:\AnypointStudio\TestCases\PlanCafetaria\Input" moveToDirectory="C:\AnypointStudio\TestCases\PlanCafetaria\Work" responseTimeout="10000" doc:name="File"/>
            <file:file-to-string-transformer doc:name="File to String"/>
            <json:object-to-json-transformer doc:name="Object to JSON"/>
            <http:request config-ref="HTTPSGetUnboxToken" path="api/login" method="POST" source="# [message.payload]" requestStreamingMode="NEVER" sendBodyMode="ALWAYS" doc:name="HTTPS">
                <http:request-builder>
                    <http:header headerName="Content-Type" value="application/json; charset=UTF-8"/>
                </http:request-builder>
            </http:request>
            <logger level="INFO" doc:name="Logger"/>
        </flow>
    </mule>

input file contain :

{

"username" : "myuser",

"password" : "mypassword"

}

any help will be appreciate,

Thanks in advance

Pascal.