"catchall" tenant id for quering

[rlex]

Is your feature request related to a problem? Please describe.
I want to utilize loki's multi-tenant functionality to automatically route logs to separate tenants and query them. It's more for accounting and separate limits than to actual ACL and permissions, so proper isolation isn't problem here. To use multi-tenant query function i need to pass all supported tenant IDs to X-Scope-OrgID header when quering. However, it quickly becomes a problem. For example, we have more than 100 namespaces that needs to be routed, or if we want to route based on team names, it's even more. As more teams/nses gets created, it needs constant manual adding to grafana's config, which requires manual intervention each time. Of course it's possible, but it's sub-optimal.

Describe the solution you'd like
Implement some kind of reserved "catchall" tenant ID (which should be explicitly enabled via loki config) that allows you to query all available tenants, if it's possible.

Describe alternatives you've considered
Can't think of anything else. Another option might be specifying tenant ID via query, but reserved __tenant_id__ only allows filtering on tenants already defined in request header.
Maybe something like
__query_tenant_id__ that works the same way as header?

Additional context
N/A