Checkpoint: deleting is working

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

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

@@ -23,8 +23,22 @@ public class ExchangeService {
     public Exchange save(Exchange exchange){
         return this.repo.save(exchange);
     }
-
+ 
+    /** 
+     * @param id Id of exchange in database
+     * @return Optional Exchange if found
+     */
+    public Optional<Exchange> getById(Long id){
+        return this.repo.findById(id);
+    } 
     
+    /** 
+     * @param entity Exchange entity which we would like to delete
+     */
+    public void deleteExchange(Exchange entity){
+        this.repo.delete(entity);
+    }
+
     /** 
      * @param assignment Assignment to trade for
      * @param group Desired group