CustomAuthenticationExtension.ReadWrite.All

const options = {
	authProvider,
};

const client = Client.init(options);

const customAuthenticationExtension = {
    '@odata.type': '#microsoft.graph.onTokenIssuanceStartCustomExtension',
    displayName: 'onTokenIssuanceStartCustomExtension',
    description: 'Fetch additional claims from custom user store',
    endpointConfiguration: {
        '@odata.type': '#microsoft.graph.httpRequestEndpoint',
        targetUrl: 'https://authenticationeventsAPI.contoso.com'
    },
    authenticationConfiguration: {
        '@odata.type': '#microsoft.graph.azureAdTokenAuthentication',
        resourceId: 'api://authenticationeventsAPI.contoso.com/a13d0fc1-04ab-4ede-b215-63de0174cbb4'
    },
    clientConfiguration: {
        timeoutInMilliseconds: 2000,
        maximumRetries: 1
    },
    claimsForTokenConfiguration: [
        {
            claimIdInApiResponse: 'DateOfBirth'
        },
        {
            claimIdInApiResponse: 'CustomRoles'
        }
    ]
};

await client.api('/identity/customAuthenticationExtensions')
	.post(customAuthenticationExtension);

Import-Module Microsoft.Graph.Identity.SignIns

$params = @{
	"@odata.type" = "#microsoft.graph.onTokenIssuanceStartCustomExtension"
	displayName = "onTokenIssuanceStartCustomExtension"
	description = "Fetch additional claims from custom user store"
	endpointConfiguration = @{
		"@odata.type" = "#microsoft.graph.httpRequestEndpoint"
		targetUrl = "https://authenticationeventsAPI.contoso.com"
	}
	authenticationConfiguration = @{
		"@odata.type" = "#microsoft.graph.azureAdTokenAuthentication"
		resourceId = "api://authenticationeventsAPI.contoso.com/a13d0fc1-04ab-4ede-b215-63de0174cbb4"
	}
	clientConfiguration = @{
		timeoutInMilliseconds = 2000
		maximumRetries = 1
	}
	claimsForTokenConfiguration = @(
		@{
			claimIdInApiResponse = "DateOfBirth"
		}
		@{
			claimIdInApiResponse = "CustomRoles"
		}
	)
}

New-MgIdentityCustomAuthenticationExtension -BodyParameter $params

# Code snippets are only available for the latest version. Current version is 1.x
from msgraph import GraphServiceClient
from msgraph.generated.models.on_token_issuance_start_custom_extension import OnTokenIssuanceStartCustomExtension
from msgraph.generated.models.http_request_endpoint import HttpRequestEndpoint
from msgraph.generated.models.azure_ad_token_authentication import AzureAdTokenAuthentication
from msgraph.generated.models.custom_extension_client_configuration import CustomExtensionClientConfiguration
from msgraph.generated.models.on_token_issuance_start_return_claim import OnTokenIssuanceStartReturnClaim
# To initialize your graph_client, see https://learn.microsoft.com/en-us/graph/sdks/create-client?from=snippets&tabs=python
request_body = OnTokenIssuanceStartCustomExtension(
	odata_type = "#microsoft.graph.onTokenIssuanceStartCustomExtension",
	display_name = "onTokenIssuanceStartCustomExtension",
	description = "Fetch additional claims from custom user store",
	endpoint_configuration = HttpRequestEndpoint(
		odata_type = "#microsoft.graph.httpRequestEndpoint",
		target_url = "https://authenticationeventsAPI.contoso.com",
	),
	authentication_configuration = AzureAdTokenAuthentication(
		odata_type = "#microsoft.graph.azureAdTokenAuthentication",
		resource_id = "api://authenticationeventsAPI.contoso.com/a13d0fc1-04ab-4ede-b215-63de0174cbb4",
	),
	client_configuration = CustomExtensionClientConfiguration(
		timeout_in_milliseconds = 2000,
		maximum_retries = 1,
	),
	claims_for_token_configuration = [
		OnTokenIssuanceStartReturnClaim(
			claim_id_in_api_response = "DateOfBirth",
		),
		OnTokenIssuanceStartReturnClaim(
			claim_id_in_api_response = "CustomRoles",
		),
	],
)

result = await graph_client.identity.custom_authentication_extensions.post(request_body)