Hi Pedro,

I do have such a file in resources/META-INF (and checked it was loaded by changing the name of the persistence-unit), with some minor differences: a different datasource name and an additional entity class :

<persistence xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xsi:schemaLocation="
http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="primary">
<jta-data-source>java:jboss/datasources/example-ds</jta-data-source>
<class>org.jboss.as.quickstarts.picketlink.angularjs.model.Person</class>
<class>org.jboss.as.quickstarts.picketlink.angularjs.security.model.entity.MyUserTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.AttributedTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.RoleTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.GroupTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.IdentityTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.RelationshipTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.RelationshipIdentityTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.PartitionTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.AttributeTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.PasswordCredentialTypeEntity</class>
<class>org.picketlink.idm.jpa.model.sample.simple.TokenCredentialTypeEntity</class>
<properties>
<!-- Properties for Hibernate -->
<property name="hibernate.hbm2ddl.auto" value="create-drop"/>
<property name="hibernate.show_sql" value="false"/>
</properties>
</persistence-unit>
</persistence>

but still the same error :

Caused by: org.picketlink.idm.config.SecurityConfigurationException: Error while creating IdentityStore [class org.picketlink.idm.jpa.internal.JPAIdentityStore] instance for configuration [org.picketlink.idm.config.JPAIdentityStoreConfiguration@56d38ca6].
at org.picketlink.idm.internal.DefaultPartitionManager.createIdentityStore(DefaultPartitionManager.java:844) [picketlink-2.7.0.Beta1-20140731.jar:]
at org.picketlink.idm.internal.DefaultPartitionManager.<init>(DefaultPartitionManager.java:225) [picketlink-2.7.0.Beta1-20140731.jar:]
... 223 more
Caused by: org.picketlink.idm.config.SecurityConfigurationException: Invalid mapping for type [class org.jboss.as.quickstarts.picketlink.angularjs.security.model.MyUser]. No entity found with a field annotated with interface org.picketlink.idm.jpa.annotations.Identifier.
at org.picketlink.idm.jpa.internal.JPAIdentityStore.checkIfAnnotationIsDefined(JPAIdentityStore.java:1990) [picketlink-2.7.0.Beta1-20140731.jar:]
at org.picketlink.idm.jpa.internal.JPAIdentityStore.validateTypeMapping(JPAIdentityStore.java:1956) [picketlink-2.7.0.Beta1-20140731.jar:]
at org.picketlink.idm.jpa.internal.JPAIdentityStore.validateConfiguration(JPAIdentityStore.java:1909) [picketlink-2.7.0.Beta1-20140731.jar:]
at org.picketlink.idm.jpa.internal.JPAIdentityStore.setup(JPAIdentityStore.java:149) [picketlink-2.7.0.Beta1-20140731.jar:]
at org.picketlink.idm.jpa.internal.JPAIdentityStore.setup(JPAIdentityStore.java:119) [picketlink-2.7.0.Beta1-20140731.jar:]
at org.picketlink.idm.internal.DefaultPartitionManager.createIdentityStore(DefaultPartitionManager.java:840) [picketlink-2.7.0.Beta1-20140731.jar:]
... 224 more