Checkpoint: return all exchanges works

Signed-off-by: Marcin Woźniak <y0rune@aol.com>

buisnesslogic/src/main/java/com/plannaplan/services/ExchangeService.java

@@ -1,5 +1,6 @@
 package com.plannaplan.services;
 
+import java.util.List;
 import java.util.Optional;
 
 import com.plannaplan.entities.Assignment;
@@ -32,6 +33,14 @@ public class ExchangeService {
         return this.repo.findById(id);
     } 
     
+    /** 
+     * @param id Id of user
+     * @return List of exchanges that belong to user
+     */
+    public List<Exchange> getByUserId(Long id){
+        return this.repo.getByUserId(id);
+    } 
+
     /** 
      * @param entity Exchange entity which we would like to delete
      */