Clarify path param naming (#32969)

In history (from some legacy frameworks), both `:name` and `name` are
supported as path path name, `:name` is an alias to `name`.

To make code consistent, now we should only use `name` but not `:name`.

Also added panic check in related functions to make sure the name won't
be abused in case some downstreams still use them.

routers/api/v1/notify/threads.go

@@ -101,7 +101,7 @@ func ReadThread(ctx *context.APIContext) {
 }
 
 func getThread(ctx *context.APIContext) *activities_model.Notification {
-	n, err := activities_model.GetNotificationByID(ctx, ctx.PathParamInt64(":id"))
+	n, err := activities_model.GetNotificationByID(ctx, ctx.PathParamInt64("id"))
 	if err != nil {
 		if db.IsErrNotExist(err) {
 			ctx.Error(http.StatusNotFound, "GetNotificationByID", err)