feat: make request ACS index configurable (#190)

* feat: make request ACS index configurable

* Apply suggestions from code review

---------

Co-authored-by: Giuseppe De Marco <demarcog83@gmail.com>

Author: tensor5

example/backends/spidsaml2.py

@@ -381,11 +381,11 @@ def authn_request(self, context, entity_id):
             # spid-testenv2 preleva l'attribute consumer service dalla authnRequest
             # (anche se questo sta già nei metadati...)
             # Imposta il consuming_service_index in base al default di ficep per le richieste ficep, oppure a '0' per le richieste spid
-            if entity_id == self.config["sp_config"]["ficep_entity_id"]:
-                authn_req.attribute_consuming_service_index = str(self.config["sp_config"]["ficep_default_acs_index"])
-            else:
-                authn_req.attribute_consuming_service_index = "0"
-
+            authn_req.attribute_consuming_service_index = str(
+                 self.config["sp_config"].get("acs_index") or
+                 self.config["sp_config"].get("ficep_default_acs_index") or
+                 "0"
+            )
             issuer = saml2.saml.Issuer()
             issuer.name_qualifier = client.config.entityid
             issuer.text = client.config.entityid

example/plugins/backends/spidsaml2_backend.yaml

@@ -76,6 +76,9 @@ config:
     entityid: '<base_url>/<name>/metadata'
     accepted_time_diff: 10
 
+    # Specify the AttributeConsumingServiceIndex attribute in the request (default 0).
+    # acs_index: 0
+
     service:
       sp:
         ui_info: