Set the "Accept" request header to the specified type, rathern than a…

[Numpsy]

…lways ApplicationJson

When doing some tests with a client for an API that returns plain text, I noticed that the Accept header on SwaggerProvider requests always seemed to be set to application/json rather than the text type specified in the OpenApi spec, and then I saw this checking if retMime is specified but then always using ApplicationJson and wondered if that's correct?

If this is an issue then maybe it could also be tested with something like

[<Route("api/[controller]")>]
[<ApiController>]
type ReturnCsvController() =
    inherit ControllerBase()

    [<HttpGet; Produces("text/csv")>]
    member this.Get() =
        if this.Request.Headers.Accept.Equals("text/csv") then
            "Hello,world" |> ActionResult<string>
        else
            ActionResult<string>(UnsupportedMediaTypeResult())

?