Gets configured context fields

Whether the response should include project-specific or root context fields in addition to the fields in the default response. When querying the root context API, `include=project` will yield a response that includes all project-specific context fields in addition to all root context fields. Conversely, when querying a project-specific context API, using `include=root` will yield a response that includes all root context fields in addition to the project-specific context fields. The other combinations have no effect, because the responses already include those fields. When including project-specific context fields via the root-level API, context fields in private projects the user does not have access to will be omitted.