Update Organizer table

src/main/java/de/dpunkt/myaktion/model/Organizer.java

 package de.dpunkt.myaktion.model;
 
+import javax.persistence.Column;
 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
@@ -35,6 +36,7 @@ public class Organizer extends DateEntity {
     private String lastName;
 
     @Pattern(regexp = ".+@.+", message = "{organizer.email.pattern}")
+    @Column(unique = true)
     private String email;
 
     @NotNull