Implement SignedEntityStore providers

Author: jpraynaud

mithril-aggregator/src/database/provider/mod.rs

@@ -2,11 +2,13 @@
 mod certificate;
 mod epoch_setting;
 mod open_message;
+mod signed_entity;
 mod signer_registration;
 mod stake_pool;
 
 pub use certificate::*;
 pub use epoch_setting::*;
 pub use open_message::*;
+pub use signed_entity::*;
 pub use signer_registration::*;
 pub use stake_pool::*;