add concurrency to categorisation lambda

infrastructure/terraform/lambda/categorisation/variables.tf

@@ -17,6 +17,11 @@ variable "image_digest" {
   description = "Image digest (sha256:...)"
 }
 
+variable "maximum_concurrency" {
+  type        = number
+  default     = 10 # null if you don't want to set it for this handler
+  description = "Maximum number of concurrent Lambda invocations from SQS (2-1000). null = no limit."
+}
 
 locals {
   image_uri = "${var.ecr_repo_url}@${var.image_digest}"