feat(router): add offset in mandate list route (#3923)

crates/router/src/db/mandate.rs

@@ -262,14 +262,22 @@ impl MandateInterface for MockDb {
             checker
         });
 
+        #[allow(clippy::as_conversions)]
+        let offset = (if mandate_constraints.offset.unwrap_or(0) < 0 {
+            0
+        } else {
+            mandate_constraints.offset.unwrap_or(0)
+        }) as usize;
+
         let mandates: Vec<storage::Mandate> = if let Some(limit) = mandate_constraints.limit {
             #[allow(clippy::as_conversions)]
             mandates_iter
+                .skip(offset)
                 .take((if limit < 0 { 0 } else { limit }) as usize)
                 .cloned()
                 .collect()
         } else {
-            mandates_iter.cloned().collect()
+            mandates_iter.skip(offset).cloned().collect()
         };
         Ok(mandates)
     }

crates/router/src/routes/mandates.rs

@@ -101,6 +101,7 @@ pub async fn revoke_mandate(
         ("created_time.gt" = Option<PrimitiveDateTime>, Query, description = "Time greater than the mandate created time"),
         ("created_time.lte" = Option<PrimitiveDateTime>, Query, description = "Time less than or equals to the mandate created time"),
         ("created_time.gte" = Option<PrimitiveDateTime>, Query, description = "Time greater than or equals to the mandate created time"),
+        ("offset" = Option<i64>, Query, description = "The number of Mandate Objects to skip when retrieving the list Mandates."),
     ),
     responses(
         (status = 200, description = "The mandate list was retrieved successfully", body = Vec<MandateResponse>),

crates/router/src/types/storage/mandate.rs

@@ -54,6 +54,9 @@ impl MandateDbExt for Mandate {
         if let Some(limit) = mandate_list_constraints.limit {
             filter = filter.limit(limit);
         }
+        if let Some(offset) = mandate_list_constraints.offset {
+            filter = filter.offset(offset);
+        }
 
         logger::debug!(query = %diesel::debug_query::<diesel::pg::Pg, _>(&filter).to_string());