doc: Update 1.12.0 release guide and Changelog (#1488)

Author: maastha

CHANGELOG.md

@@ -11,10 +11,11 @@
 
 **Bug Fixes**
 
+- **Breaking Change**: Fixes an issue where removing `collectionName` from user role doesn't work [\#1471](https://github.com/mongodb/terraform-provider-mongodbatlas/pull/1471) ([marcosuma](https://github.com/marcosuma)).
+  - Note: As a result, `mongodbatlas_database_user` no longer requires `roles.collection_name` attribute and doesn't support an empty `collection_name`. You should remove any usage of `roles.collection_name = ""` in configurations for this resource when you upgrade to this version. For more details see:  https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/guides/1.12.0-upgrade-guide. 
 - Populates `total_count` in `mongodbatlas_alert_configurations` data source  [\#1476](https://github.com/mongodb/terraform-provider-mongodbatlas/pull/1476) ([lantoli](https://github.com/lantoli))
 - Improves error handling for `cloud_backup_schedule` resource. [\#1474](https://github.com/mongodb/terraform-provider-mongodbatlas/pull/1474) ([marcosuma](https://github.com/marcosuma))
 - Handles incorrect ids when importing `alert_configuration` or `project_ip_access_list` resources [\#1472](https://github.com/mongodb/terraform-provider-mongodbatlas/pull/1472) ([lantoli](https://github.com/lantoli))
-- Fix when removing `collectionName` from user role [\#1471](https://github.com/mongodb/terraform-provider-mongodbatlas/pull/1471) ([marcosuma](https://github.com/marcosuma))
 - Changelog Spelling Fixes  [\#1457](https://github.com/mongodb/terraform-provider-mongodbatlas/pull/1457) ([Zuhairahmed](https://github.com/Zuhairahmed))
 - Adds `mongodbatlas_database_user` username parameter OIDC footnote in docs [\#1458](https://github.com/mongodb/terraform-provider-mongodbatlas/pull/1458) ([Zuhairahmed](https://github.com/Zuhairahmed))
 

website/docs/guides/1.12.0-upgrade-guide.html.markdown

@@ -14,6 +14,9 @@ The Terraform MongoDB Atlas Provider version 1.12.0 has a number of new and exci
 - You can now manage [Atlas Resource Tags](https://www.mongodb.com/docs/atlas/tags/)  in [`mongodbatlas_cluster`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/cluster), [`mongodbatlas_advanced_cluster`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/advanced_cluster), and [`mongodbatlas_serverless_instance`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/serverless_instance). 
 - You can now programmatically retrieve Atlas Organizational User details with [`mongodbatlas_atlas_user`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/data-sources/atlas_user) and [`mongodbatlas_atlas_users`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/data-sources/atlas_users) data sources 
 
+**Breaking Changes:**   
+- Fixes `mongodbatlas_database_user` to not require `roles.collection_name` attribute and not support empty `collection_name`. You should remove any usage of `roles.collection_name = ""` in configurations for this resource when you upgrade to this version.
+
 
 **Deprecations and Removals:**   
 - Deprecation of `labels` attribute in `mongodbatlas_cluster` and `mongodbatlas_advanced_cluster` resources.