Username updated to email for autherization

Author: MonuChaudhary14

src/main/java/org/spacehub/entities/User/User.java

@@ -90,13 +90,9 @@ public String getPassword() {
 
   @Override
   public String getUsername() {
-    if (this.username != null && !this.username.isBlank()) {
-      return this.username;
-    }
-    return "Enter your username";
+    return email;
   }
 
-
   @Override
   public boolean isAccountNonLocked() {
     return !locked;