Relax IAM role restrictions on BQ datasets (hashicorp#857)

Signed-off-by: Modular Magician <magic-modules@google.com>

google-beta/resource_bigquery_dataset.go

@@ -6,7 +6,6 @@ import (
 	"regexp"
 
 	"github.com/hashicorp/terraform/helper/schema"
-	"github.com/hashicorp/terraform/helper/validation"
 	"google.golang.org/api/bigquery/v2"
 )
 
@@ -138,9 +137,8 @@ func resourceBigQueryDataset() *schema.Resource {
 				Elem: &schema.Resource{
 					Schema: map[string]*schema.Schema{
 						"role": {
-							Type:         schema.TypeString,
-							Optional:     true,
-							ValidateFunc: validation.StringInSlice([]string{"OWNER", "WRITER", "READER"}, false),
+							Type:     schema.TypeString,
+							Optional: true,
 						},
 						"domain": {
 							Type:     schema.TypeString,

website/docs/r/bigquery_dataset.html.markdown

@@ -111,8 +111,11 @@ The `access` block supports the following fields (exactly one of `domain`,
 even though they are marked optional):
 
 * `role` - (Required unless `view` is set) Describes the rights granted to
-    the user specified by the other member of the access object. The following
-    string values are supported: `READER`, `WRITER`, `OWNER`.
+    the user specified by the other member of the access object. 
+    Primitive, Predefined and custom roles are supported.
+    Predefined roles that have equivalent primitive roles are swapped 
+    by the API to their Primitive counterparts, and will show a diff post-create. 
+    See [official docs](https://cloud.google.com/bigquery/docs/access-control).
 
 * `domain` - (Optional) A domain to grant access to.