use prefix in group role assigment

[stempher]

It is not convenient to use a prefix "p:" in the resource teamcity_group_role_assigment parameter project_id. Maybe use a locator?

resource "teamcity_group_role_assignment" "test_group_2_project_dev_test_project" {
  group_key  = teamcity_group.test_group_2.id
  role_id    = "PROJECT_DEVELOPER"
  project_id = "p:${teamcity_project.test_project.id}"
}