[breaking] Terraform 0.12 compatibility (breaks 0.11 compatibility) (#105)

[breaking] Terraform 0.12 compatibility (breaks 0.11 compatibility)### Summary
This PR adds the changes over and above #104 to make cztack compatible with 0.12. Specifically:
* Removing brackets around arguments that are already supposed to be lists. In some rare cases (involving calculated fields), this doesn't work properly in 0.11, so considering it breaking.
* Removes use of terraform-docs; terraform-docs is incompatible with Terraform 0.12 (see terraform-docs/terraform-docs#62)
* Uses the new dynamic block syntax to be able to pass dynamically generated blocks that coincidentally worked in 0.11 but are incompatible with 0.12.

### Test Plan
Testing via corresponding shared-infra PR successfully passing.

Author: mbarrien

.travis.yml

@@ -1,17 +1,17 @@
 language: go
 go:
-- 1.10.3
+- 1.12.5
 sudo: false
 dist: trusty
 cache: pip
 install:
 # terraform
-- wget -t 10 -O terraform.zip https://releases.hashicorp.com/terraform/0.11.8/terraform_0.11.8_linux_amd64.zip
+- wget -t 10 -O terraform.zip https://releases.hashicorp.com/terraform/0.12.5/terraform_0.12.5_linux_amd64.zip
 - unzip terraform.zip
 - mv terraform ~/bin/
 - chmod +x ~/bin/terraform
 # terraform-provider-bless
-- wget -t 10 -O terraform-provider-bless.tar https://github.com/chanzuckerberg/terraform-provider-bless/releases/download/v0.2.5/terraform-provider-bless_0.2.5_linux_amd64.tar.gz
+- wget -t 10 -O terraform-provider-bless.tar https://github.com/chanzuckerberg/terraform-provider-bless/releases/download/v0.2.8/terraform-provider-bless_0.2.8_linux_amd64.tar.gz
 - tar -C ~/bin -xzf terraform-provider-bless.tar
 # terraform-docs
 - wget -t 10 -O terraform-docs https://github.com/segmentio/terraform-docs/releases/download/v0.6.0/terraform-docs-v0.6.0-linux-amd64
@@ -27,8 +27,9 @@ jobs:
   include:
   - stage: check
     script: make lint
-  - stage: check
-    script: make check-docs
+  # terraform-docs is incompatible with 0.12 for now
+  # - stage: check
+  #   script: make check-docs
   - stage: check
     before_script:
     - aws configure set aws_access_key_id     $CI1_AWS_ACCESS_KEY_ID     --profile

Gopkg.lock

@@ -2,6 +2,8 @@
 
 Cztack (pronounced "stack") is CZI's collection of Terraform modules. We use these as way to scale our infrastructure work.
 
+These modules are compatible with Terraform 0.12 and up.
+
 ## Design Principles
 
 More TODO here

Gopkg.toml

@@ -12,7 +12,7 @@ locals {
 
 resource "aws_acm_certificate" "cert" {
   domain_name               = "${var.cert_domain_name}"
-  subject_alternative_names = ["${keys(var.cert_subject_alternative_names)}"]
+  subject_alternative_names = "${keys(var.cert_subject_alternative_names)}"
   validation_method         = "DNS"
   tags                      = "${local.tags}"
 
@@ -36,5 +36,5 @@ resource "aws_route53_record" "cert_validation" {
 
 resource "aws_acm_certificate_validation" "cert" {
   certificate_arn         = "${aws_acm_certificate.cert.arn}"
-  validation_record_fqdns = ["${aws_route53_record.cert_validation.*.fqdn}"]
+  validation_record_fqdns = "${aws_route53_record.cert_validation.*.fqdn}"
 }

README.md

@@ -23,7 +23,9 @@ module "aurora" {
   port                = 5432
   instance_class      = "${var.instance_class}"
   instance_count      = "${var.instance_count}"
-  backtrack_window    = 0                            # not supported yet
+
+  # backtrack_window not supported yet
+  backtrack_window    = 0
   skip_final_snapshot = "${var.skip_final_snapshot}"
   kms_key_id          = "${var.kms_key_id}"
   apply_immediately   = "${var.apply_immediately}"

aws-acm-cert/main.tf

@@ -21,7 +21,7 @@ resource "aws_security_group" "rds" {
     from_port   = "${var.port}"
     to_port     = "${var.port}"
     protocol    = "tcp"
-    cidr_blocks = ["${var.ingress_cidr_blocks}"]
+    cidr_blocks = "${var.ingress_cidr_blocks}"
   }
 
   lifecycle {
@@ -81,7 +81,14 @@ resource "aws_rds_cluster_parameter_group" "db" {
   family      = "${var.engine}${var.engine_version}"
   description = "RDS default cluster parameter group"
 
-  parameter = ["${var.rds_cluster_parameters}"]
+  dynamic "parameter" {
+    for_each = var.rds_cluster_parameters
+    content {
+      name         = parameter.value.name
+      value        = parameter.value.value
+      apply_method = parameter.value.apply_method
+    }
+  }
 
   lifecycle {
     ignore_changes = ["family"]
@@ -94,7 +101,14 @@ resource "aws_db_parameter_group" "db" {
   name   = "${local.name}"
   family = "${var.engine}${var.engine_version}"
 
-  parameter = ["${var.db_parameters}"]
+  dynamic "parameter" {
+    for_each = var.db_parameters
+    content {
+      name         = parameter.value.name
+      value        = parameter.value.value
+      apply_method = parameter.value.apply_method
+    }
+  }
 
   lifecycle {
     ignore_changes = ["family"]

aws-aurora-postgres/main.tf

@@ -5,7 +5,7 @@ locals {
 resource "aws_cloudwatch_log_group" "group" {
   name = "${local.log_group_name}"
 
-  tags {
+  tags = {
     project   = "${var.project}"
     env       = "${var.env}"
     service   = "${var.service}"

aws-aurora/main.tf

@@ -27,7 +27,7 @@ module "default-vpc" {
 
   default_sg_lockdown = true
 
-  providers {
+  providers = {
     "aws" = "aws.us-west-1"
   }
 }