post
https://api.qfp.quantnetwork.net/api/tenants//groups
Creates a group with a stable key (e.g. #mlro) that policies
reference. The key must match ^#[a-z][a-z0-9_]{0,62}$, is unique
per tenant (case-insensitively; a duplicate is 409) and is
immutable after creation. The group starts ACTIVE with no
members.
Requires group:manage, and the path tenant must equal the caller's
tenant_id claim.

