FIX: Create-drop databse. Add ManyToMany annotation

src/Server/src/main/java/greenify/server/data/model/User.java

@@ -13,6 +13,8 @@ import javax.persistence.GeneratedValue;
 import javax.persistence.GenerationType;
 import javax.persistence.Id;
 import javax.persistence.Table;
+import java.util.*;
+import javax.persistence.*;
 import javax.validation.constraints.NotNull;
 
 @Entity
@@ -21,7 +23,9 @@ import javax.validation.constraints.NotNull;
 public class User {
 
     @Id
+    @NotNull
     @GeneratedValue(strategy = GenerationType.AUTO)
+//    @Column(name = "id")
     private Long id;
 
     @NotNull
@@ -36,6 +40,10 @@ public class User {
     @ElementCollection
     private Map<String,String> footPrintInputs = new HashMap<>();
 
+    @ManyToMany
+    @JoinColumn
+    private Collection<User> friends;
+
     public User() {}
 
     /**
@@ -103,6 +111,10 @@ public class User {
         this.footPrintInputs = footPrintInputs;
     }
 
+    public ArrayList<User> getFriends(){
+        return (ArrayList<User>)this.friends;
+    }
+
     public void setFootPrint(Float footPrint) {
         this.footPrint = footPrint;
     }