Add examples for Group SAML links

Author: mhodgson

examples/resources/gitlab_group_saml_link/import.sh

@@ -0,0 +1,2 @@
+# GitLab group saml links can be imported using an id made up of `group_id:saml_group_name`, e.g.
+terraform import gitlab_group_saml_link.test "12345:samlgroupname1"

examples/resources/gitlab_group_saml_link/resource.tf

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+resource "gitlab_group_saml_link" "test" {
+  group_id        = "12345"
+  access_level    = "Developer"
+  saml_group_name = "samlgroupname1"
+}