split MintDatabase into separate narrower scoped traits

- MintKeysDatabase
- MintQuotesDatabase
- MintProofsDatabase
- MintSignaturesDatabase

This commit splits the MintDatabase trait with 30+ methods into a series
of smaller traits, each dedicate to a specific subsystem of the mint
service.

crates/cdk-common/src/database/mod.rs

@@ -5,10 +5,14 @@ mod mint;
 #[cfg(feature = "wallet")]
 mod wallet;
 
-#[cfg(feature = "mint")]
-pub use mint::Database as MintDatabase;
 #[cfg(all(feature = "mint", feature = "auth"))]
 pub use mint::MintAuthDatabase;
+#[cfg(feature = "mint")]
+pub use mint::{
+    Database as MintDatabase, KeysDatabase as MintKeysDatabase,
+    ProofsDatabase as MintProofsDatabase, QuotesDatabase as MintQuotesDatabase,
+    SignaturesDatabase as MintSignaturesDatabase,
+};
 #[cfg(feature = "wallet")]
 pub use wallet::Database as WalletDatabase;