Crowd doesn't update hibernate's User/Group caches with Attribute changes

The new reverse mapping for InternalUserAttributes to InternalUser added in CWD-4016 causes problems with Hibernate's caches, because we aren't explicitly updating the user's attributes in the hibernate mapped entity, which Hibernate uses to populate/update its caches. The same thing applies for groups.

Problematic hibernate definition added in InternalUser.hbm.xml:

    <class name="com.atlassian.crowd.model.user.InternalUser" table="cwd_user" lazy="true">
        <!-- snipped out irrelevant details -->
        <set name="attributes" lazy="true" inverse="true">
            <key column="user_id" not-null="true"/>

            <one-to-many class="com.atlassian.crowd.model.user.InternalUserAttribute"/>
        </set>
    </class&gt;

This means that when we create or update an InternalUserAttribute for a given user then it has to be added to InternalUser.attributes. For example:

    private void addAttribute(InternalUser user, String attributeName, String attributeValue)
    {
        InternalUserAttribute attribute = new InternalUserAttribute(user, attributeName, attributeValue);
        session().save(attribute);
        // 2 lines below are what we need to do now
        user.attributes.add(attribute)
        session().save(user);
    }

In theory this doesn't actually save to the database; it just updates hibernate's caches. Of course we need to do it in all places that we modify a user's (or group's) attributes.

Consequences of not doing so are that hibernate will give different views onto user attributes depending on how you ask the question; i.e. inconsistent data.

Reported by bryan.turner after upgrading Stash to the latest Crowd & seeing strange behaviour under load.