Custom Connectors - API url + body

Hi,

I am working on a custom connector for PowerBI to get Data from an API. I'd like to specify both the url and the json body

I created a working version that only takes the url as parameter. Everything else is hardcoded.

MyQueryType = type function (
url as (Uri.Type meta [
        Documentation.FieldCaption = "Instance Uri",
        Documentation.FieldDescription = "Enter your Instance url",
        Documentation.SampleValues = { "http://my-instance.westeurope.cloudapp.azure.com" }
        ])
) as table meta [
        Documentation.Name = "My Query",
        Documentation.LongDescription = "Long Desc"
        ];

APIRequestImpl = (url as text) as table =>

    let
        url_full = url&"/library/api/invocation",
        headers = [#"Content-Type"="application/json"],
        body = "{
                ""dataframe"": """",
                ""input"": ""{\""sensor.id\"":\""abc-bourse_cotations_abcng\"",\""sensor.channel\"":\""Ouverture\"",\""start_date\"":\""2010-01-01\"",\""end_date\"":\""2030-01-01\""}"",
                ""technical_name"": ""TSDataCleaning""
            }",
        response = Json.Document(Web.Contents(url_full, [Content=Text.ToBinary(body), Headers=headers])),
        toTable = Table.FromList(response[preprocessing_data], Splitter.SplitByNothing(), null, null, ExtraValues.Error),
        expand = Table.ExpandRecordColumn(toTable, "Column1", {"timestamps", "value", "imputed_value","denoised_value","is.missing","is.anomaly"}, {"timestamps", "value", "imputed_value","denoised_value","is.missing","is.anomaly"})
               
    in
        expand;

But when I try to add the request body parameter, It get this error:

My code:

MyQueryType = type function (
url as (Uri.Type meta [
        Documentation.FieldCaption = "Loamics instance Uri",
        Documentation.FieldDescription = "Enter your LOAMICS Instance url",
        Documentation.SampleValues = { "http://dtles-loamics-demo-dns-mmburs3gaabwc.westeurope.cloudapp.azure.com" }
        ]),
request_body as (type text meta [
        Documentation.FieldCaption = "Request body",
        Documentation.FieldDescription = "Enter your request body",
        Documentation.SampleValues = { "{}" }])
) as table meta [
        Documentation.Name = "My Query",
        Documentation.LongDescription = "Long Desc"
        ];

APIRequestImpl = (url as text, request_body as text) as table =>

    let
        url_full = url&"/library/api/invocation",
        headers = [#"Content-Type"="application/json"],
        body = "{
                ""dataframe"": """",
                ""input"": ""{\""sensor.id\"":\""abc-bourse_cotations_abcng\"",\""sensor.channel\"":\""Ouverture\"",\""start_date\"":\""2010-01-01\"",\""end_date\"":\""2030-01-01\""}"",
                ""technical_name"": ""TSDataCleaning""
            }",
        response = Json.Document(Web.Contents(url_full, [Content=Text.ToBinary(body), Headers=headers])),
        toTable = Table.FromList(response[preprocessing_data], Splitter.SplitByNothing(), null, null, ExtraValues.Error),
        expand = Table.ExpandRecordColumn(toTable, "Column1", {"timestamps", "value", "imputed_value","denoised_value","is.missing","is.anomaly"}, {"timestamps", "value", "imputed_value","denoised_value","is.missing","is.anomaly"})
               
    in
        expand;

Thanks in advance