JSON Schema references - Example Code not working

[Pandera5]

Hello,

Iam trying to get references working with json schemas. Basically I want to have two schemas:

Product:

{
    "$schema": "http://json-schema.org/draft-07/schema#",
    "$id": "product.json"
    "additionalProperties": false,
    "type": "object",
    "properties": {
        "accountId": {
            "description": "Unique identifier for the associated account.",
            "type": "string"
        },
        "productId": {
            "description": "Unique identifier for the product.",
            "type": "string"
        },
        "priceOptions": {
            "description": "List of price options for the product.",
            "type": "array",
            "items": {"$ref": "popDetails.json"}
        }
    },
    "required": [
        "productId",
        "accountId",
        "priceOptions"
    ]
}

and the referenced popDetails.json:

{
    "$schema": "http://json-schema.org/draft-07/schema#",
    "$id": "popDetails.json"
    "additionalProperties": false,
    "type": "object",
    "properties": {
        "popId": {
            "description": "Unique identifier for the price option.",
            "type": "string"
        },
        "popChargePeriodType": {
            "type": "string",
            "enum": [
                "MONTHLY",
                "YEARLY",
                "NONE"
            ]
        }
    },
    "required": [
        "popId",
        "popRecurringChargePeriodType"
    ]
}

With this example, when I want to produce a message via quarkus and smallrye messaging, I get the following error:
ERROR [io.api.reg.res.ERCache] (smallrye-kafka-producer-thread-0) Failed to update cache value for key: ArtifactCoordinates [groupId=test, artifactId=product, version=null]: com.networknt.schema.InvalidSchemaException: /$id: 'product.json' is not a valid $id

When I try to set an URL like http://example.com/schemas/product as $id I get an FileNotFoundException.

I tried the example from examples/serdes-with-references but it didnt work too with the exception: ERROR: Failed to load json schema from https://example.com/city.json java.net.UnknownHostException: example.com

I am using the apicurio image: quay.io/apicurio/apicurio-registry:3.0.6

Could anyone give me a solution or tips to my problem?

Thanks