Move creation of scoped db connection based on workspace to a middleware

Example

```
pub async fn create(
state: web::Data,
_auth: AuthenticatedRequest,
ws: Workspace,
body: web::Json,
) -> Result {
let trigger = TriggerType::from_str_val(&body.trigger)
.ok_or_else(|| AppError::InvalidRequest(format!("Invalid trigger: {}", body.trigger)))?;

let mut conn = kronos_common::db::scoped::scoped_connection(&state.pool, &ws.0.schema_name)
.await
.map_err(AppError::from)?;

```