Implement SingleSignatureStore provider

Author: jpraynaud

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

@@ -5,6 +5,7 @@ mod open_message;
 mod signed_entity;
 mod signer;
 mod signer_registration;
+mod single_signature;
 mod stake_pool;
 
 pub use certificate::*;
@@ -13,4 +14,5 @@ pub use open_message::*;
 pub use signed_entity::*;
 pub use signer::*;
 pub use signer_registration::*;
+pub use single_signature::*;
 pub use stake_pool::*;