update doc comments

Author: timidri

plans/add_replica.pp

@@ -1,12 +1,11 @@
-# @summary Add a replica to a PE architecture or replace an existing one.
-# Supported use cases:
-#  1: the replica is gone
-#  2: there is no replica
-#  both use cases: we have a fresh new VM we want to provision the replica to.
+# @summary Replace a replica host for a Standard or Large architecture.
+#   Supported use cases:
+#   1: The existing replica is broken, we have a fresh new VM we want to provision the replica to.
+#      The new replica should have the same certname as the broken one.
 # @param primary_host - The hostname and certname of the primary Puppet server
 # @param replica_host - The hostname and certname of the replica VM
 # @param replica_postgresql_host - The hostname and certname of the host with the replica PE-PosgreSQL database. 
-# Can be a separate host in an XL architecture, or undef in Standard or Large.
+#   Can be a separate host in an XL architecture, or undef in Standard or Large.
 plan peadm::add_replica(
   # Standard or Large
   Peadm::SingleTargetSpec           $primary_host,