PowerBI Power Query "We cannot apply field access to the type Binary"

Thank you lbendlin!

That worked, I have one more doubt...I'm getting the following error

An error occurred in the ‘get_token’ query. Expression.Error: The 'Authorization' header is only supported when connecting anonymously. These headers can be used with all authentication types: Accept, Accept-Charset, Accept-Encoding, Accept-Language, Cache-Control, Content-Type, If-Modified-Since, Prefer, Range, Referer

However, if I select to login anonymously... it wants my credentials:

My code:

let gettoken=() =>
    let
    JWT="<my_token>",
    Data= Web.Contents("https://api.github.com/app/installations/<id>/access_tokens", 
                      [
                        Headers=[
                                    #"Accept"="application/vnd.github+json",
                                    #"Authorization"="Bearer" & JWT,
                                    #"X-GitHub-Api-Version"="2022-11-28",
                                    #"Content-Type"="application/x-www-form-urlencoded"                                 
                        ]])
        ,token=Json.Document(Data)[token]
in
    token   
in gettoken

If needed I can open another post.