Make IDENTITY function work with joined columns

Feature Request

Q	A
New Feature	yes
RFC	no
BC Break	no

Summary

On https://www.doctrine-project.org/projects/doctrine-orm/en/2.7/reference/dql-doctrine-query-language.html#dql-select-examples it is said

the IDENTITY() DQL function also works for composite primary keys

But if these keys are part of another association they won’t be found in fields but in associations mapping, hence throwing.

Example

Given the following entities

class Contract
{
    /**
     * @ORM\ManyToOne(targetEntity="Agent")
     * @ORM\Id
     */
    private $agent;

    /**
     * @ORM\ManyToOne(targetEntity="Agency")
     * @ORM\Id
     */
    private $agency;
}

class Estate
{
    /**
     * @ORM\ManyToOne(targetEntity="Contract")
     * @ORM\JoinColumns({
     *  @ORM\JoinColumn(name="contract_agent_id", referencedColumnName="agent_id"),
     *  @ORM\JoinColumn(name="contract_agency_id", referencedColumnName="agency_id"),
     * })
     */
    protected $contract;
}

I expected to be able to write IDENTITY(estate.contract, 'agent_id').

Is this something that could be implemented?