Better signature errors messages.

lib/pleroma/web/activity_pub/activity_pub_controller.ex

@@ -34,9 +34,14 @@ def inbox(%{assigns: %{valid_signature: true}} = conn, params) do
   end
 
   def inbox(conn, params) do
+    if !(String.contains(conn.req_headers["signature"] || "", params["actor"])) do
+      Logger.info("Signature not from author, relayed message, ignoring.")
+    else
       Logger.info("Signature error.")
       Logger.info("Could not validate #{params["actor"]}")
       Logger.info(inspect(conn.req_headers))
+    end
+
     json(conn, "ok")
   end