Add account_type=organization support to the usage metrics
endpoint. When requested, the API filters users by a shared
OIDC claim (account_id_key/account_id_value) and returns
aggregated storage across all matching users.
Add handling of account_id_key/account_id_value pair, allowing
filtering on allowed parameters in a more generic way. At the
moment `account_email` filter is still needed.
Also include the context of the entitlement in the /entitlements
response.