Introduce cdk-sql-common

The primary purpose of this new crate is to have a common and shared codebase
for all SQL storage systems. It would force us to write standard SQL using best
practices for all databases.

This crate has been extracted from #878

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

@@ -0,0 +1,53 @@
+//! Database traits definition
+
+use std::fmt::Debug;
+
+use cdk_common::database::Error;
+
+use crate::stmt::{Column, Statement};
+
+/// Database Executor
+///
+/// This trait defines the expectations of a database execution
+#[async_trait::async_trait]
+pub trait DatabaseExecutor: Debug + Sync + Send {
+    /// Database driver name
+    fn name() -> &'static str;
+
+    /// Executes a query and returns the affected rows
+    async fn execute(&self, statement: Statement) -> Result<usize, Error>;
+
+    /// Runs the query and returns the first row or None
+    async fn fetch_one(&self, statement: Statement) -> Result<Option<Vec<Column>>, Error>;
+
+    /// Runs the query and returns the first row or None
+    async fn fetch_all(&self, statement: Statement) -> Result<Vec<Vec<Column>>, Error>;
+
+    /// Fetches the first row and column from a query
+    async fn pluck(&self, statement: Statement) -> Result<Option<Column>, Error>;
+
+    /// Batch execution
+    async fn batch(&self, statement: Statement) -> Result<(), Error>;
+}
+
+/// Database transaction trait
+#[async_trait::async_trait]
+pub trait DatabaseTransaction<'a>: Debug + DatabaseExecutor + Send + Sync {
+    /// Consumes the current transaction committing the changes
+    async fn commit(self) -> Result<(), Error>;
+
+    /// Consumes the transaction rolling back all changes
+    async fn rollback(self) -> Result<(), Error>;
+}
+
+/// Database connector
+#[async_trait::async_trait]
+pub trait DatabaseConnector: Debug + DatabaseExecutor + Send + Sync {
+    /// Transaction type for this database connection
+    type Transaction<'a>: DatabaseTransaction<'a>
+    where
+        Self: 'a;
+
+    /// Begin a new transaction
+    async fn begin(&self) -> Result<Self::Transaction<'_>, Error>;
+}