Need a Keruald YAML library available in a keruald/yaml package, that can handle custom tags.

First use case will be workspace configuration for Obsidian Workspace:

orbeonDatabase:
  engine: Keruald\Database\Engines\PostgreSQLPDOEngine
  host: !env ORBEON_DB_HOST
  username: !env ORBEON_DB_USER
  password: !env ORBEON_DB_PASSWORD
  database: forms
  fetch_mode: *fetch_mode_assoc

Basically, we could work with Symfony parser, and create handlers for TaggedValue.

Parser should accept !env or !<tag:keruald.nasqueron.org,2025:env> to read $_ENV or $_SERVER