[Feature]: Add sea-orm support for shuttle_shared_db

[joshua-mo-143]

Describe the feature

A feature that allows users to provision a sea_orm Postgres connection from shuttle_shared_db.

Suggestion or Example of how the feature would be used

#[shuttle_runtime]
async fn main(
#[shuttle_shared_db::Postgres] db: sea_orm::DatabaseConnection<SqlxPostgresPoolConnection>
) -> shuttle_axum::ShuttleAxum {
  // .. etc
}

Duplicate declaration

• I have searched the issues and this feature has not been requested before.