Added monitoring, limited concurent connections (#245)

* reduced the default, and added environment override.

* Using parse is more stable and doesn't fail CI this time :P

* Added support for monitoring
This support is currently basic, but it can be improved later down the road.

* Forgot scheduler file

* Added health check

* Cargo fix

* Update cargo.lock to avoid action fails.

Co-authored-by: Geometrically <18202329+Geometrically@users.noreply.github.com>

src/health/status.rs

@@ -0,0 +1,16 @@
+use sqlx::{PgPool};
+use actix_web::web;
+
+pub async fn test_database(postgres: web::Data<PgPool>) -> Result<(), sqlx::Error> {
+    let mut transaction = postgres.acquire().await?;
+    let result = sqlx::query(
+            "
+            SELECT 1
+            "
+        ).execute(&mut transaction)
+        .await;
+    match result {
+        Ok(_) => Ok(()),
+        Err(e) => Err(e)
+    }
+}