Keycloak - trying to map nested arrays (returned in the userProfile of the IDP) to a multi-values attribute

Question

I am using Keycloak to connect to an external Identity Providers via OIDC.

Step 1 : I created standard mappers « Attribute Importer » to retrieve attributes using the claims supported by the IDP.

Examples of simple mappings :

• Name of my attribute in Keycloak : lastName
• Claim returned by the IDP : name

->Easy, that works.

Step 2 : I need to perform more complex mapping. That's where I need help.

The IDP has added in the userInfo nested arrays that I have to parse. From this parsing, I need to retrieve multiple values and return this to the client through the Keycloak JWT token.

In a nutshell what I need to do :

• in the userInfo returned by the IDP, I get nested arrays such as :

"claim": { // the claim
        "id": 1,
        "arrayOfAttributes": {
            "attribute1": XX,
            "attribute2": [
                {
                    "**attributeIWant1**": 12,
                    "dateXX": "2023-01-01",
                    "attributeYY": XXX,
                },
            "attribute3": [
                {
                    "**attributeIWant2**": 13,
                    "dateXX": "2023-01-01",
                    "attributeYY": XXX,
                },
            "attribute4": [
                {
                    "**attributeIWant3**": 14,
                    "dateXX": "2023-01-01",
                    "attributeYY": XXX,
                },
         },
}

• I would like to retrieve the values from attributeIWant1, attributeIWant2 and attributeIWant3
• map these values to a multi-valued attribute in Keycloak (I read that the delimiter should be « ## » but not sure),
• and have this multi-valued attribute returned in the JWT token to the client.

-> Can you please guide me to the best/simplest solution ? Can I do that using the UI ? Or do I need to code a custom mapping ?

Thanks for your help,