Allow config endpoint as reader endpoint output (#245)

Required when running in cluster mode as there is no reader endpoint

Co-authored-by: Kevin <belay.00.theorem@icloud.com>

main.tf

@@ -115,8 +115,8 @@ locals {
   reader_endpoint_serverless = try(aws_elasticache_serverless_cache.default[0].reader_endpoint[0].address, null)
   reader_endpoint_cluster    = try(aws_elasticache_replication_group.default[0].reader_endpoint_address, null)
   reader_endpoint_instance   = try(aws_elasticache_replication_group.default[0].reader_endpoint_address, null)
-  # Use the serverless reader endpoint if serverless mode is enabled, otherwise use the cluster reader endpoint, otherwise use the instance reader endpoint
-  reader_endpoint_address = coalesce(local.reader_endpoint_serverless, local.reader_endpoint_cluster, local.reader_endpoint_instance)
+  # Use the serverless reader endpoint if serverless mode is enabled, otherwise use the cluster reader endpoint, otherwise use the instance reader endpoint, otherwise use the endpoint address
+  reader_endpoint_address = coalesce(local.reader_endpoint_serverless, local.reader_endpoint_cluster, local.reader_endpoint_instance, local.endpoint_address)
 }
 
 resource "aws_elasticache_subnet_group" "default" {