Add PostgreSQL support for mint and wallet (#878)

* Add PostgreSQL support for mint and wallet

* Fixed bug to avoid empty calls `get_proofs_states`

* Fixed SQL bug

* Avoid redudant clone()

* Add more tests for the storage layer

* Minor enhacements

* Add a generic function to execute db operations

This function would log slow operations and log errors

* Provision a postgres db for tests

* Update deps for msrv

* Add postgres to pipeline

* feat: add psgl to example and docker

* feat: db url fmt

---------

Co-authored-by: thesimplekid <tsk@thesimplekid.com>

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

@@ -182,7 +182,7 @@ where
 
     /// Begin a transaction
     async fn begin(conn: &mut W) -> Result<(), Error> {
-        query("BEGIN")?.execute(conn).await?;
+        query("START TRANSACTION")?.execute(conn).await?;
         Ok(())
     }