Allow kms to receive a custom alias name

When setting up the telemetry module for multiple environments, a new
kms_alias is created for SNS, but it's not possible to create multiple
aliases with the same name. This allows to have a custom name.

aws/telemetry/main.tf

@@ -11,6 +11,8 @@ module "sns_topics" {
       "${source}-${severity}"
     ]
   ])
+
+  kms_alias_name = var.kms_alias_name
 }
 
 module "prometheus_workspace" {

aws/telemetry/modules/sns-topics/variables.tf

@@ -15,6 +15,11 @@ variable "sns_topic_names" {
   type        = list(string)
 }
 
+variable "kms_alias_name" {
+  description = "KMS alias name for SNS topics"
+  type        = string
+}
+
 variable "tags" {
   description = "Tags to be applied to created resources"
   type        = map(string)

aws/telemetry/variables.tf

@@ -68,3 +68,9 @@ variable "tags" {
   type        = map(string)
   default     = {}
 }
+
+variable "kms_alias_name" {
+  description = "KMS alias name for SNS topics"
+  type        = string
+  default     = "alias/sns-alarm-topics"
+}