Allow for allow_overwrite functionality (#21)

I want to manage some existing records with Terraform, so need this
functionality which switches the action to an UPSERT, from CREATE.

README.md

@@ -119,6 +119,7 @@ Available targets:
 | Name | Description | Type | Default | Required |
 |------|-------------|:----:|:-----:|:-----:|
 | aliases | List of aliases | list(string) | - | yes |
+| allow_overwrite | Allow creation of this record in Terraform to overwrite an existing record, if any. This does not affect the ability to update the record in Terraform and does not prevent other resources within Terraform or manual Route 53 changes outside Terraform from overwriting this record. false by default. This configuration is not recommended for most environments | bool | `false` | no |
 | enabled | Set to false to prevent the module from creating any resources | bool | `true` | no |
 | evaluate_target_health | Set to true if you want Route 53 to determine whether to respond to DNS queries | bool | `false` | no |
 | ipv6_enabled | Set to true to enable an AAAA DNS record to be set as well as the A record | bool | `false` | no |
@@ -190,6 +191,10 @@ We deliver 10x the value for a fraction of the cost of a full-time engineer. Our
 
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@@ -305,6 +310,7 @@ Check out [our other projects][github], [follow us on twitter][twitter], [apply
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docs/terraform.md

@@ -3,6 +3,7 @@
 | Name | Description | Type | Default | Required |
 |------|-------------|:----:|:-----:|:-----:|
 | aliases | List of aliases | list(string) | - | yes |
+| allow_overwrite | Allow creation of this record in Terraform to overwrite an existing record, if any. This does not affect the ability to update the record in Terraform and does not prevent other resources within Terraform or manual Route 53 changes outside Terraform from overwriting this record. false by default. This configuration is not recommended for most environments | bool | `false` | no |
 | enabled | Set to false to prevent the module from creating any resources | bool | `true` | no |
 | evaluate_target_health | Set to true if you want Route 53 to determine whether to respond to DNS queries | bool | `false` | no |
 | ipv6_enabled | Set to true to enable an AAAA DNS record to be set as well as the A record | bool | `false` | no |

main.tf

@@ -6,10 +6,11 @@ data "aws_route53_zone" "default" {
 }
 
 resource "aws_route53_record" "default" {
-  count   = var.enabled ? length(compact(var.aliases)) : 0
-  zone_id = data.aws_route53_zone.default[0].zone_id
-  name    = compact(var.aliases)[count.index]
-  type    = "A"
+  count           = var.enabled ? length(compact(var.aliases)) : 0
+  zone_id         = data.aws_route53_zone.default[0].zone_id
+  name            = compact(var.aliases)[count.index]
+  allow_overwrite = var.allow_overwrite
+  type            = "A"
 
   alias {
     name                   = var.target_dns_name
@@ -19,10 +20,11 @@ resource "aws_route53_record" "default" {
 }
 
 resource "aws_route53_record" "ipv6" {
-  count   = var.enabled && var.ipv6_enabled ? length(compact(var.aliases)) : 0
-  zone_id = data.aws_route53_zone.default[0].zone_id
-  name    = compact(var.aliases)[count.index]
-  type    = "AAAA"
+  count           = var.enabled && var.ipv6_enabled ? length(compact(var.aliases)) : 0
+  zone_id         = data.aws_route53_zone.default[0].zone_id
+  name            = compact(var.aliases)[count.index]
+  allow_overwrite = var.allow_overwrite
+  type            = "AAAA"
 
   alias {
     name                   = var.target_dns_name

variables.tf

@@ -48,3 +48,9 @@ variable "ipv6_enabled" {
   default     = false
   description = "Set to true to enable an AAAA DNS record to be set as well as the A record"
 }
+
+variable "allow_overwrite" {
+  type        = bool
+  default     = false
+  description = "Allow creation of this record in Terraform to overwrite an existing record, if any. This does not affect the ability to update the record in Terraform and does not prevent other resources within Terraform or manual Route 53 changes outside Terraform from overwriting this record. false by default. This configuration is not recommended for most environments"
+}