member.created

If a user was invited via email address to a membership, then a 'member.created' webhook will be dispatched.
If the domain or IP address of a user was added to the membership subscription, then once that user logs in/registers, you would receive both 'member.created' and 'member.activated' webhooks.
{
  "type": "member.created",
  "id": "evt_CmuntPK8JxcYAxEa7rOgJvul",
  "created": 1655725565,
  "data": {
    "object": {
      "object": "member",
      "address_id": null,
      "id": null,
      "invitation_email": "[email protected]",
      "plan": {
        "object": "plan",
        "id": 110,
        "object_id": "plan_LTDbz9mgLw3JTI",
        "active": "active",
        "amount": 10000,
        "currency": "cad",
        "domains": null,
        "entitlements": null,
        "group_owner_plan_id": null,
        "interval": "year",
        "interval_count": 1,
        "nickname": "cool plan 2",
        "name_internal": "cool plan 2",
        "type":  "membership",
        "name_internal": null,
        "trial_period_days": 0,
        "ip_addresses": null,
        "auto_renew": false,
        "shipments_per_interval": null,
        "product": {
          "object": "product",
          "id": 9,
          "object_id": "prod_LTC9K8BwjLEKbz",
          "type": "service",
          "active": "active",
          "address_required": true,
          "description": "Group membership",
          "livemode": false,
          "is_hidden": null,
          "name": "Group membership",
          "name_internal": null,
          "package_dimensions": null,
          "shippable": null,
          "statement_descriptor": "Group membership",
          "unit_label": null
        }
      },
      "site_id": 1,
      "status": "pending",
      "subscription": {
        "id": 28,
        "object_id": "sub_1KmHAOHPqVSuBrMIGOHuzNN0",
        "site_id": 1,
        "address_id": null,
        "backdate_start_date": null,
        "billing": "send_invoice",
        "billing_cycle_anchor": "2022-04-08T12:43:56.000000Z",
        "cancel_at": "2023-04-08T12:43:56.000000Z",
        "cancel_at_period_end": 1,
        "canceled_at": "2022-04-08T12:43:56.000000Z",
        "canceled_by_email": null,
        "canceled_by_type": null,
        "cancel_reason": null,
        "created": "2022-04-08T12:43:56.000000Z",
        "current_period_end": "2023-04-08T12:43:56.000000Z",
        "current_period_start": "2022-04-08T12:43:56.000000Z",
        "days_until_due": 30,
        "ended_at": null,
        "quantity": 1,
        "shipments_remaining": null,
        "source": "Email",
        "start_date": "2022-04-08T12:43:56.000000Z",
        "status": "past_due",
        "trial_end": null,
        "trial_start": null,
        "shipments_undeliverable": false,
        "shipments_suspended_until": null,
        "is_gift_donor": null,
        "is_gift_recipient": null,
        "gift_code": null,
        "is_redeemed": null,
        "gift_recipient_email": null,
        "gift_recipient_first_name": null,
        "gift_recipient_last_name": null,
        "gift_notification_sent": 0,
        "gift_start_date": null,
        "gift_message": null,
        "gift_donor_subscription_id": null,
        "agency_id": null
      },
      "subscription_id": 28,
      "user_id": null
    }
  }
}