Creates a new account associated with the group. Only available for eDocSync subscriptions.

Creating an office (organisational unit): To create an office, include parent_id in the request body. The parent must be a top-level account within the same group — it cannot itself be an office. When parent_id is set, tin_value and tin_scheme are inherited from the parent and must not be provided; sending either field returns 422 Unprocessable Entity.