Opentext Content Server

I have used documents in OpenText from Power BI via the OpenText REST API... but the problem I have is I need to hard code the API credentials in the Power Query code and I haven't found a way to integrate with Power BI's credential manager. The Power Query I used to open an Excel file from OpenText was (substitute in the username, password and appropriate OpenText API URLs and document ID for your org):

let
    GetJson = Web.Contents("https://<opentext auth server>/authentication/credentials",
        [
            Headers = [#"Content-Type"="application/json"],
            Content = Text.ToBinary("{""user_name"":""<user>"", ""password"":""<password>""}")
        ]
    ),
    FormatAsJson = Json.Document(GetJson),
    Ticket = FormatAsJson[ticket],
    DocID = "1234567",
    ExcelFile = Web.Contents("https://<opentext api server>/api/v1/nodes/" & DocID & "/content",
        [
            Headers = [#"OTDSTicket"=Ticket]
        ]
    ),
    ExcelWorkbook = Excel.Workbook(ExcelFile)
in
    ExcelWorkbook

If someone has a better way that doesn't have hard coded credentials I'd really appreciate that.