feat: improve internal sql interface

Switches from rusqlite to sqlx to have a fully async based interface
to sqlite.

Co-authored-by: B. Petersen <r10s@b44t.com>
Co-authored-by: Hocuri <hocuri@gmx.de>
Co-authored-by: link2xt <link2xt@testrun.org>

src/error.rs

@@ -1,5 +1,9 @@
 //! # Error handling
 
+#[derive(Debug, thiserror::Error)]
+#[error("Out of Range")]
+pub struct OutOfRangeError;
+
 #[macro_export]
 macro_rules! ensure_eq {
     ($left:expr, $right:expr) => ({