aptly mirror parametrization

PROD-15379

Change-Id: Icff58138405245e968d63539ec7b0df2a313b6fd
diff --git a/aptly/server/mirror/debian/cassandra.yml b/aptly/server/mirror/debian/cassandra.yml
index 846df4e..3a19e84 100644
--- a/aptly/server/mirror/debian/cassandra.yml
+++ b/aptly/server/mirror/debian/cassandra.yml
@@ -1,18 +1,22 @@
 parameters:
   _param:
     apt_mk_version: stable
+    mirror_cassandra-21x_source: http://www.apache.org/dist/cassandra/debian
+    mirror_cassandra-21x_distribution: 21x
+    mirror_cassandra-21x_components: main
+    mirror_cassandra-21x_gpgkeys:
+      - F758CE318D77295D
+      - 2B5C1B00
+      - 0353B12C
   aptly:
     server:
       mirror:
         cassandra-21x:
-          source: http://www.apache.org/dist/cassandra/debian
-          distribution: 21x
-          components: main
+          source: ${_param:mirror_cassandra-21x_source}
+          distribution: ${_param:mirror_cassandra-21x_distribution}
+          components: ${_param:mirror_cassandra-21x_components}
           architectures: amd64
-          gpgkeys:
-            - F758CE318D77295D
-            - 2B5C1B00
-            - 0353B12C
+          gpgkeys: ${_param:mirror_cassandra-21x_gpgkeys}
           publisher:
             component: extra
             distributions: