Southwest Power Pool Temporary AAR Exceptions API

A [Temporary AAR Exception](https://trolie.energy/concepts#temporary-aar-exception) isprovided by the Ratings Provider when a Ratings Obligation cannot befulfilled, due to some temporary operating condition impacting the relatedpower system resource. This could occur in various scenarios: * An equipment failure. * An unforeseen condition on a related part of the power grid. * Some ambient condition that is not part of the model is heating the line, like a wildfire. * Something in the surrounding environment is affecting the amount that a line is allowed to sag. For example, this may occur for lines over rivers when very large ships pass under themA Temporary AAR Exception serves two main purposes: documenting the reasonfor the exception and providing a temporary rating value set. It is employedin three distinct circumstances:1. Firstly, Order 881 mandates documentation and archival of all use of alternate ratings in lieu of AARs. Ratings Providers should continue to provide real-time and forecast ratings for the affected resource, but these should match the rating provided with the Temporary AAR Exception while the latter is in effect. This temporary rating, and the reason that it occurred, must be captured in history regardless of the provided ratings. The reason and the end date of the effective window may be updated after the object has been created, up to a configurable threshold. If the Ratings Providers provides ratings that deviate from the static Temporary AAR Exception rating, the Clearinghouse Provider must decide whether to use those or the static rating. The Clearinghouse Provider advise its Ratings Providers on how it will choose ahead of time. This specification recommends using the dynamic rating provided, but it does not mandate it.2. Secondly, Temporary AAR Exceptions apply when the Clearinghouse Provider is generating forecast rating proposals on behalf of the Ratings Provider, e.g., when lookup tables are provided ahead of time by the Ratings Provider. Since there is no external ratings, the Clearinghouse Provider wouldn't otherwise know that a temporary static rating is needed. 3. Finally, for facilities where dynamic ratings are provided, it is possible that a communications outage or other issue could prevent the Clearinghouse Provider from receiving the dynamic ratings. In this case, the Clearinghouse Provider would use a Temporary AAR Exception rating.