Set a more restrictive cidr range, no public ingressing

[JohnVeni]

Fix the following tfsec report :

Results #1-7 CRITICAL Network ACL rule allows ingress from public internet. (7 similar results)
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
  subnets.tf:44
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
   36    resource "aws_network_acl_rule" "allow_all_inbound" {
   37      for_each = aws_network_acl.this
   38    
   39      network_acl_id = each.value.id
   40      rule_number    = 100
   41      egress         = false
   42      protocol       = -1
   43      rule_action    = "allow"
   44  [   cidr_block     = "0.0.0.0/0" ("0.0.0.0/0")
   45    }
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
  Individual Causes
  - subnets.tf:36-45 (aws_network_acl_rule.allow_all_inbound[0])
  - subnets.tf:36-45 (aws_network_acl_rule.allow_all_inbound[6])
  - subnets.tf:36-45 (aws_network_acl_rule.allow_all_inbound[2])
  - subnets.tf:36-45 (aws_network_acl_rule.allow_all_inbound[1])
  - subnets.tf:36-45 (aws_network_acl_rule.allow_all_inbound[4])
  - subnets.tf:36-45 (aws_network_acl_rule.allow_all_inbound[3])
  - subnets.tf:36-45 (aws_network_acl_rule.allow_all_inbound[5])
────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
          ID aws-ec2-no-public-ingress-acl
      Impact The ports are exposed for ingressing data to the internet
  Resolution Set a more restrictive cidr range

  More Information
  - https://aquasecurity.github.io/tfsec/v1.28.5/checks/aws/ec2/no-public-ingress-acl/
  - https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/network_acl_rule#cidr_block
─────────────────────────────────────────────────────────────────────────────────────────────────────────────

[AndrNgg]

@JohnVeni

I like the idea of making the network module more secure. However, we need to be careful with the complexity that it might bring in the future in regard to troubleshooting.

I prefer leaving NACLS open since it's an optional security measure. Restrict with network ACL And handle all inbound and outbound network security through Security groups.

In short, the SG update in your PR is fine with me but not the NACL one as I would like to keep things simple.