fix: Make root_block_device.tags default to null

Fixes #440. Without it, if root_block_device is defined without a tags
key, and if enable_volume_tags isn't set to false, a conflict is created
because main.tf:219 defines volume_tags to be at least { Name = ... }
and the root block device gets tags as {}. Making the default null works
around that.

Author: lucasvuotto

README.md

@@ -255,7 +255,7 @@ No modules.
 | <a name="input_private_ip"></a> [private\_ip](#input\_private\_ip) | Private IP address to associate with the instance in a VPC | `string` | `null` | no |
 | <a name="input_putin_khuylo"></a> [putin\_khuylo](#input\_putin\_khuylo) | Do you agree that Putin doesn't respect Ukrainian sovereignty and territorial integrity? More info: https://en.wikipedia.org/wiki/Putin_khuylo! | `bool` | `true` | no |
 | <a name="input_region"></a> [region](#input\_region) | Region where the resource(s) will be managed. Defaults to the Region set in the provider configuration | `string` | `null` | no |
-| <a name="input_root_block_device"></a> [root\_block\_device](#input\_root\_block\_device) | Customize details about the root block device of the instance. See Block Devices below for details | <pre>object({<br/>    delete_on_termination = optional(bool)<br/>    encrypted             = optional(bool)<br/>    iops                  = optional(number)<br/>    kms_key_id            = optional(string)<br/>    tags                  = optional(map(string), {})<br/>    throughput            = optional(number)<br/>    size                  = optional(number)<br/>    type                  = optional(string)<br/>  })</pre> | `null` | no |
+| <a name="input_root_block_device"></a> [root\_block\_device](#input\_root\_block\_device) | Customize details about the root block device of the instance. See Block Devices below for details | <pre>object({<br/>    delete_on_termination = optional(bool)<br/>    encrypted             = optional(bool)<br/>    iops                  = optional(number)<br/>    kms_key_id            = optional(string)<br/>    tags                  = optional(map(string))<br/>    throughput            = optional(number)<br/>    size                  = optional(number)<br/>    type                  = optional(string)<br/>  })</pre> | `null` | no |
 | <a name="input_secondary_private_ips"></a> [secondary\_private\_ips](#input\_secondary\_private\_ips) | A list of secondary private IPv4 addresses to assign to the instance's primary network interface (eth0) in a VPC. Can only be assigned to the primary network interface (eth0) attached at instance creation, not a pre-existing network interface i.e. referenced in a `network_interface block` | `list(string)` | `null` | no |
 | <a name="input_security_group_description"></a> [security\_group\_description](#input\_security\_group\_description) | Description of the security group | `string` | `null` | no |
 | <a name="input_security_group_egress_rules"></a> [security\_group\_egress\_rules](#input\_security\_group\_egress\_rules) | Egress rules to add to the security group | <pre>map(object({<br/>    cidr_ipv4                    = optional(string)<br/>    cidr_ipv6                    = optional(string)<br/>    description                  = optional(string)<br/>    from_port                    = optional(number)<br/>    ip_protocol                  = optional(string, "tcp")<br/>    prefix_list_id               = optional(string)<br/>    referenced_security_group_id = optional(string)<br/>    tags                         = optional(map(string), {})<br/>    to_port                      = optional(number)<br/>  }))</pre> | <pre>{<br/>  "ipv4_default": {<br/>    "cidr_ipv4": "0.0.0.0/0",<br/>    "description": "Allow all IPv4 traffic",<br/>    "ip_protocol": "-1"<br/>  },<br/>  "ipv6_default": {<br/>    "cidr_ipv6": "::/0",<br/>    "description": "Allow all IPv6 traffic",<br/>    "ip_protocol": "-1"<br/>  }<br/>}</pre> | no |

variables.tf

@@ -278,7 +278,7 @@ variable "root_block_device" {
     encrypted             = optional(bool)
     iops                  = optional(number)
     kms_key_id            = optional(string)
-    tags                  = optional(map(string), {})
+    tags                  = optional(map(string))
     throughput            = optional(number)
     size                  = optional(number)
     type                  = optional(string)