Re-branch from 651 due to conflict of docs fixes (#654)

-Adds an upgrade and info guide for 1.2
-Adds a clarifying comment to the project parameter api_key_id doc page

Approved already in #651

Author: themantissa

website/docs/guides/1.2.0-upgrade-guide.html.markdown

@@ -1,4 +1,4 @@
----
+--
 layout: "mongodbatlas"
 page_title: "MongoDB Atlas Provider 1.2.0: Upgrade and Information Guide"
 sidebar_current: "docs-mongodbatlas-guides-120-upgrade-guide"
@@ -12,8 +12,14 @@ The Terraform MongoDB Atlas Provider version 1.2.0 has a number of new and excit
 
 New Features:
 
-* You can now manage private link endpoints for Data Lake and Online Archive with [`private_link_endpoint_adl`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/private_link_endpoint_adl).
+* Now supports Private Link for Atlas Data Lake and Online Archive [`mongodbatlas_privatelink_endpoint_service_adl`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/privatelink_endpoint_service_adl)
+* You can now pause clusters [`mongodbatlas_cluster`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/cluster)
+* You can now add an existing API key to a project [`mongodbatlas_project`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/project)
+* Adds version_release_system to the [`mongodbatlas_cluster`](https://registry.terraform.io/providers/mongodb/mongodbatlas/latest/docs/resources/cluster) resource and data source
+
+Changes:
 
+1.2.0 also includes general improvements and bug fixes. See the [CHANGELOG](https://github.com/mongodb/terraform-provider-mongodbatlas/blob/master/CHANGELOG.md) for more specific information.
 
 ### Helpful Links
 

website/docs/r/project.html.markdown

@@ -60,14 +60,12 @@ Teams attribute is optional
   * `GROUP_DATA_ACCESS_READ_ONLY`
   * `GROUP_CLUSTER_MANAGER`
 
-
 ~> **NOTE:** Project created by API Keys must belong to an existing organization.
 
 ### Programmatic API Keys
 api_keys allows one to assign an existing organization programmatic API key to a Project. The api_keys attribute is optional.
 
-
-* `api_key_id` - (Required) The unique identifier of the Programmatic API key you want to associate with the Project.  The Programmatic API key and Project must share the same parent organization.
+* `api_key_id` - (Required) The unique identifier of the Programmatic API key you want to associate with the Project.  The Programmatic API key and Project must share the same parent organization.  Note: this is not the `publicKey` of the Programmatic API key but the `id` of the key. See [Programmatic API Keys](https://docs.atlas.mongodb.com/reference/api/apiKeys/) for more.
 
 * `role_names` - (Required) List of Project roles that the Programmatic API key needs to have. Ensure you provide: at least one role and ensure all roles are valid for the Project.  You must specify an array even if you are only associating a single role with the Programmatic API key.
  The following are valid roles: