Update CHANGELOG.md for hashicorp#31112

CHANGELOG.md

@@ -36,7 +36,9 @@ BREAKING CHANGES:
 * resource/aws_medialive_multiplex_program: The `statemux_settings` attribute has been removed. Use `statmux_settings` argument instead ([#31034](https://github.com/hashicorp/terraform-provider-aws/issues/31034))
 * resource/aws_neptune_cluster: `snapshot_identifier` change now properly forces replacement ([#29409](https://github.com/hashicorp/terraform-provider-aws/issues/29409))
 * resource/aws_networkmanager_core_network: Removed `policy_document` argument -- use `aws_networkmanager_core_network_policy_attachment` resource instead ([#30875](https://github.com/hashicorp/terraform-provider-aws/issues/30875))
+* resource/aws_rds_cluster: The `engine` argument is now required and has no default ([#31112](https://github.com/hashicorp/terraform-provider-aws/issues/31112))
 * resource/aws_rds_cluster: `snapshot_identifier` change now properly forces replacement ([#29409](https://github.com/hashicorp/terraform-provider-aws/issues/29409))
+* resource/aws_rds_cluster_instance: The `engine` argument is now required and has no default ([#31112](https://github.com/hashicorp/terraform-provider-aws/issues/31112))
 * resource/aws_redshift_cluster: With the retirement of EC2-Classic the `cluster_security_groups` attribute has been removed ([#30966](https://github.com/hashicorp/terraform-provider-aws/issues/30966))
 * resource/aws_route: `instance_id` can no longer be set in configurations. Use `network_interface_id` instead, for example, setting `network_interface_id` to `aws_instance.test.primary_network_interface_id`. ([#30804](https://github.com/hashicorp/terraform-provider-aws/issues/30804))
 * resource/aws_route_table: `route.*.instance_id` can no longer be set in configurations. Use `route.*.network_interface_id` instead, for example, setting `network_interface_id` to `aws_instance.test.primary_network_interface_id`. ([#30804](https://github.com/hashicorp/terraform-provider-aws/issues/30804))
@@ -62,6 +64,8 @@ NOTES:
 * resource/aws_neptune_cluster: Changes to the `snapshot_identifier` attribute will now trigger a replacement, rather than an in-place update. This corrects the previous behavior which resulted in a successful apply, but did not actually restore the cluster from the designated snapshot. ([#29409](https://github.com/hashicorp/terraform-provider-aws/issues/29409))
 * resource/aws_networkmanager_core_network: Update configurations to use the `aws_networkmanager_core_network_policy_attachment` resource instead of the `policy_document` argument ([#30875](https://github.com/hashicorp/terraform-provider-aws/issues/30875))
 * resource/aws_rds_cluster: Changes to the `snapshot_identifier` attribute will now trigger a replacement, rather than an in-place update. This corrects the previous behavior which resulted in a successful apply, but did not actually restore the cluster from the designated snapshot. ([#29409](https://github.com/hashicorp/terraform-provider-aws/issues/29409))
+* resource/aws_rds_cluster: Configurations not including the `engine` argument must be updated to include `engine` as it is now required. Previously, not including `engine` was equivalent to `engine = "aurora"` and created a MySQL-5.6-compatible cluster ([#31112](https://github.com/hashicorp/terraform-provider-aws/issues/31112))
+* resource/aws_rds_cluster_instance: Configurations not including the `engine` argument must be updated to include `engine` as it is now required. Previously, not including `engine` was equivalent to `engine = "aurora"` and created a MySQL-5.6-compatible cluster instance ([#31112](https://github.com/hashicorp/terraform-provider-aws/issues/31112))
 * resource/aws_route: Since `instance_id` can no longer be set in configurations, use `network_interface_id` instead. For example, set `network_interface_id` to `aws_instance.test.primary_network_interface_id`. ([#30804](https://github.com/hashicorp/terraform-provider-aws/issues/30804))
 * resource/aws_route_table: Since `route.*.instance_id` can no longer be set in configurations, use `route.*.network_interface_id` instead. For example, set `network_interface_id` to `aws_instance.test.primary_network_interface_id`. ([#30804](https://github.com/hashicorp/terraform-provider-aws/issues/30804))