Set ApplicationInsights RequestTelemetry operation name suitable for grouping (just like https://github.com/Microsoft/ApplicationInsights-aspnetcore/blob/ead65975f0fa27650b40983265bad05fdea16a95/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs#L38)

Giraffe.ApplicationInsights.fs

module Giraffe.ApplicationInsights

open Giraffe
open Microsoft.ApplicationInsights.DataContracts

let private setRoutingMetadata action : HttpHandler =
    fun next ctx ->
        let action' = ctx.Request.Method + " " + action
        ctx.Request.RouteValues.["controller"] <- "Giraffe"
        ctx.Request.RouteValues.["action"] <- action'
        let telemetry = ctx.Features.Get<RequestTelemetry>()
        if not <| isNull telemetry then telemetry.Name <- action'
        next ctx

let routef (path: PrintfFormat<_,_,_,_, 'T>) (routeHandler: 'T -> HttpHandler) : HttpHandler =
    setRoutingMetadata path.Value >=> (routef path routeHandler)

let route (path: string) : HttpHandler =
    setRoutingMetadata path >=> (route path)