Починил БД и лабу :)

spring_online_calculator/src/main/java/premium_store/model/TankLevel.java

@@ -4,7 +4,7 @@ import javax.persistence.*;
 import java.util.Objects;
 
 @Entity
-public class Level {
+public class TankLevel {
     @Id
     @GeneratedValue(strategy = GenerationType.AUTO)
     private Long id;
@@ -12,10 +12,10 @@ public class Level {
     @Column(nullable = false)
     private int level;
 
-    public Level() {
+    public TankLevel() {
     }
 
-    public Level(int level) {
+    public TankLevel(int level) {
         this.level = level;
     }
 
@@ -42,7 +42,7 @@ public class Level {
         if (o == null || getClass() != o.getClass())
             return false;
 
-        Level level = (Level) o;
+        TankLevel level = (TankLevel) o;
 
         return Objects.equals(id, level.id);
     }