Add sofia gateway parameter "destination-prefix"

FS-5497 add sofia gateway parameter destination-prefix in case you need to send Invites to your provider with prefix only to this gateway

src/mod/endpoints/mod_sofia/mod_sofia.c

@@ -4319,9 +4319,9 @@ static switch_call_cause_t sofia_outgoing_channel(switch_core_session_t *session
 		}
 
 		if (!strchr(dest, '@')) {
-			tech_pvt->dest = switch_core_session_sprintf(nsession, "sip:%s@%s", dest, sofia_glue_strip_proto(gateway_ptr->register_proxy));
+			tech_pvt->dest = switch_core_session_sprintf(nsession, "sip:%s%s@%s", gateway_ptr->destination_prefix, dest, sofia_glue_strip_proto(gateway_ptr->register_proxy));
 		} else {
-			tech_pvt->dest = switch_core_session_sprintf(nsession, "sip:%s", dest);
+			tech_pvt->dest = switch_core_session_sprintf(nsession, "sip:%s%s", gateway_ptr->destination_prefix, dest);
 		}
 
 		if ((host = switch_core_session_strdup(nsession, tech_pvt->dest))) {

src/mod/endpoints/mod_sofia/mod_sofia.h

@@ -478,6 +478,7 @@ struct sofia_gateway {
 	char *register_context;
 	char *expires_str;
 	char *register_url;
+	char *destination_prefix;
 	char *from_domain;
 	sofia_transport_t register_transport;
 	uint32_t freq;

src/mod/endpoints/mod_sofia/sofia.c

@@ -3315,6 +3315,7 @@ static void parse_gateways(sofia_profile_t *profile, switch_xml_t gateways_tag)
 			gateway->ob_calls = 0;
 			gateway->ib_failed_calls = 0;
 			gateway->ob_failed_calls = 0;
+			gateway->destination_prefix = "";
 
 			if ((x_params = switch_xml_child(gateway_tag, "variables"))) {
 				param = switch_xml_child(x_params, "variable");
@@ -3416,6 +3417,10 @@ static void parse_gateways(sofia_profile_t *profile, switch_xml_t gateways_tag)
 					outbound_proxy = val;
 				} else if (!strcmp(var, "distinct-to")) {
 					distinct_to = switch_true(val);
+				} else if (!strcmp(var, "destination-prefix")) {
+					if (!zstr(val)) {
+						gateway->destination_prefix = switch_core_strdup(gateway->pool, val);
+					}
 				} else if (!strcmp(var, "rfc-5626")) {
 					rfc_5626 = switch_true(val);
 				} else if (!strcmp(var, "reg-id")) {