Use unique index rather than constraint when using formula [like lower(column)]

src/main/java/io/ebeaninternal/server/deploy/IndexDefinition.java

@@ -35,6 +35,22 @@ public class IndexDefinition {
     this.platforms = null;
   }
 
+  /**
+   * Return true if this can be used as a unique constraint.
+   */
+  public boolean isUniqueConstraint() {
+    return unique && noColumnFormulas();
+  }
+
+  private boolean noColumnFormulas() {
+    for (String column : columns) {
+      if (column.contains("(")) {
+        return false;
+      }
+    }
+    return true;
+  }
+
   /**
    * Return true if this is a unique constraint.
    */