Provide access to multiple "named databases"

[isedwards]

Extend roll-based access control to provide access to "named databases", e.g. a user may have access to:

• api.opencdms.org/test/climsoft/v1/observation-finals/
• api.opencdms.org/prod/climsoft/v1/observation-finals/

This assumes that configuring database access control will be via an OpenCDMS API at the root (like /auth/) rather than via the Climsoft API (/db_name/climsoft/v1/...)

see: /src/opencdms_api/climsoft_rbac_config.py