Set headers for http streams

[Quackdoc]

The app works great, but some http streams will send you to an error 404 unless you set headers, I have a patch here that shows how it can be set fine.

diff --git a/receiver/src/pipeline.rs b/receiver/src/pipeline.rs
index 612781e..af1dfee 100644
--- a/receiver/src/pipeline.rs
+++ b/receiver/src/pipeline.rs
@@ -56,6 +56,9 @@ impl Pipeline {
                 if factory.name() == "rtspsrc" {
                     elem.set_property("latency", 0u32);
                 }
+                if factory.name() == "souphttpsrc" {
+                    elem.set_property("user-agent", "Mozilla/5.0 (X11; Linux x86_64; rv:142.0) Gecko/20100101 Firefox/142.0");
+                }
             }
 
             None

[MAlba124]

This should ideally be sent by the sender as a header in the FCast play request. This receiver currently ignores it but I'll try to support this in the near future.