Use some default fetchPlan in case nested attribute of the dataContainer has no fetch-plan associated

[mariodavid]

Scenario

In relation to this issue in Jmix Studio: https://youtrack.haulmont.com/issue/JST-2582

When there is no fetchPlan set in the attribute of the data container like this (via XML):

<instance id="productDc"
                  class="de.diedavids.jmix.rys.product.Product">
    <fetchPlan extends="_base">
        <property name="prices"/>
    </fetchPlan>
    <loader/>
    <collection id="pricesDc" property="prices"/>
</instance>

Here <property name="prices"/> misses fetchPlan="someFetchPlan". It is unspecified what is loaded in this scenario. Apperently neither _base nor _instance_name is used. Instead no attributes are loaded.

Improvement

When not adding any fetch plan to the XML (or programmatically), there should be a default fetch plan that is used. Probably it should be the _base fetch plan, since it is most likely that the this fetch plan is considered to be the "default".

[reznikova21]

1.2.0-SNAPSHOT - verified