postgresql_role: Add roles attribute.

* This allows to grant roles to the role we are managing.

CHANGELOG.md

@@ -1,12 +1,18 @@
-## 0.2.2 (Unreleased)
+## 0.3.0 (Unreleased)
+
+FEATURES:
+
+* `postgresql_role`: Add `roles` attribute.
 
 ## 0.2.1 (February 28, 2019)
+
 BUG FIXES:
 
 * `provider`: Add a `superuser` setting to fix role password update when provider is not connected as a superuser.
   ([#66](https://github.com/terraform-providers/terraform-provider-postgresql/pull/66))
 
 ## 0.2.0 (February 21, 2019)
+
 FEATURES:
 
 * Add `database_username` in provider configuration to manage [user name maps](https://www.postgresql.org/docs/current/auth-username-maps.html) (e.g.: needed for Azure)

postgresql/helpers.go

@@ -7,6 +7,8 @@ import (
 	"database/sql"
 
 	"github.com/hashicorp/errwrap"
+
+	"github.com/hashicorp/terraform/helper/schema"
 	"github.com/lib/pq"
 )
 
@@ -91,3 +93,11 @@ func revokeRoleMembership(db *sql.DB, role, member string) error {
 	}
 	return nil
 }
+
+func pgArrayToSet(arr pq.ByteaArray) *schema.Set {
+	s := make([]interface{}, len(arr))
+	for i, v := range arr {
+		s[i] = string(v)
+	}
+	return schema.NewSet(schema.HashString, s)
+}