Add support for shared VPC ingress shared security group rules

[mikeatlas]

Hi uMotif,

Thanks for sharing this module. My redis cluster needs Shared VPC ingress security group support, and as such, the input variable security_group_ids is not able to reference the existing SG in the shared VPC. Instead, I had to reference some outputs and create the ingress rules myself. Perhaps this could be integrated into future versions of your module:

resource "aws_security_group_rule" "shared_ingress" {
  count                    = length(var.security_group_ids)
  description              = "From allowed SGs"
  type                     = "ingress"
  to_port                  = module.elasticache_redis.elasticache_port
  from_port                = module.elasticache_redis.elasticache_port
  protocol                 = "tcp"
  source_security_group_id = element(var.security_group_ids, count.index)
  security_group_id        = module.elasticache_redis.security_group_id
}

This specifically has source_security_group_id input, which can support shared security group ingress source traffic.

Thanks!

[Ohid25]

Thanks for the contribution @mikeatlas 🙌 ! This request has now been fulfilled and included in the 3.1.0 release.

[mikeatlas]

Awesome. Thank you!