Get variable from Azure

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Hello,
I setup Shibboleth IdP 4.3.1 as Azure proxy and it work fine.I want, after user login with his/her Azure credentials, to search in local LDAP for this user, but using Azure UUID.
In attribute-resolver.xml I try this:

<DataConnector id="myLDAP" xsi:type="LDAPDirectory" ...
    <ReturnAttributes>* +</ReturnAttributes>
    <InputAttributeDefinition ref="schacSn2" />

    <FilterTemplate>
        <![CDATA[
                uid=$resolutionContext.principal
        ]]>
    </FilterTemplate>
...
</DataConnector>

(Works, but search for user principal name)
Just for sample, this works too:

<![CDATA[       entryUUID=3d746326-7256-103d-9366-6beb72b64c1c]]>

I can see corect Azure UUID (with schacSn2, 1.3.6.1.4.1.25178.1.2.7) and entryUUID values in SP after login. The additional information I get from LDAP is also visible in the above examples.

In FilterTemplate, this gives an error or returns an empty value:

entryUUID=$schacSn2entryUUID=$schacSn2.get(0)entryUUID=$schacSn2.getValues().get(0)
How to set up FilterTemplate to get Azure UUID and search in LDAP ?
Thank you!