Hi there,
It sounds like you have two tenants (company1 and company2). Do you want them to both have access to the same data, or do you want to restrict data access per tenant?
Kibana doesn't support a true multi-tenant architecture. Instead, it supports a multi-instance architecture, in which you can create multiple Kibana instances, each of which is configured to point to a different configuration index. In Kibana's kibana.yml config file, you can edit the kibana.index setting to be a unique index, which will be created if it doesn't already exist.
Once you have multiple kibana instances running (each with its own index), you can point each tenant to a unique index. In this situation, they'll both have access to the same Elasticsearch data. If you want to restrict the data each tenant has access to, you can use X-Pack Security to define users and roles to do so. For reference, a similar solution was proposed in Does ElasticSearch/Kibana Support Multi Tenancy?.
Does this make sense?
I'm not sure I understand your question about your proxy server. What is it you're trying to do? Are you trying to use your existing authentication service to authenticate users for Kibana?
Thanks,
CJ