removed “attributeName” from annotation as this breaks EclipseLink JPA

Author: jricher

openid-connect-common/src/main/java/org/mitre/oauth2/model/AuthenticationHolderEntity.java

@@ -252,7 +252,7 @@ public void setResponseTypes(Set<String> responseTypes) {
 )
 @Column(name="val")
 @MapKeyColumn(name="extension")
-@Convert(attributeName="value", converter=SerializableStringConverter.class)
+@Convert(converter=SerializableStringConverter.class)
 public Map<String, Serializable> getExtensions() {
 return extensions;
 }