doc: Adds 1.34.0 upgrade guide (#3309)

* doc: Adds 1.34.0 upgrade guide

* fix: link to description attribute

* doc: Update 1.34.0 upgrade guide with link to changelog

Author: EspenAlbert

docs/guides/1.34.0-upgrade-guide.md

@@ -0,0 +1,23 @@
+---
+page_title: "Upgrade Guide 1.34.0"
+---
+
+# MongoDB Atlas Provider 1.34.0: Upgrade and Information Guide
+
+The Terraform MongoDB Atlas Provider version 1.34.0 has a number of new and exciting features.
+
+## New Resources, Data Sources, and Features
+
+- `mongodbatlas_database_user` resource and data sources now support the new `description` attribute. To learn more, see the [mongodbatlas_database_user](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/database_user#description-1) resource documentation.
+
+- `mongodbatlas_maintenance_window` resource and data sources now support the new `protected_hours` and `time_zone_id` attributes. To learn more, see the [mongodbatlas_maintenance_window](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/maintenance_window) resource documentation.
+
+- The release also includes general improvements, bug fixes, and several key documentation updates. See the [CHANGELOG](https://github.com/mongodb/terraform-provider-mongodbatlas/blob/master/CHANGELOG.md) for more specific information.
+
+## Helpful Links
+
+* [Report bugs](https://github.com/mongodb/terraform-provider-mongodbatlas/issues)
+
+* [Request Features](https://feedback.mongodb.com/forums/924145-atlas?category_id=370723)
+
+* [Contact Support](https://docs.atlas.mongodb.com/support/) covered by MongoDB Atlas support plans, Developer and above.