* config: support environment variable macros in peer apiKeys
Add ${env.VAR_NAME} substitution for peer apiKey fields, consistent
with existing env macro support for model fields and global apiKeys.
- Add env macro substitution for peers.{name}.apiKey in LoadConfigFromReader
- Add tests for peer apiKey env substitution
- Update config.example.yaml to show env macro usage
* config: support macros in peer apiKey and filters
Extend macro substitution to peer configuration fields:
- peers.{name}.apiKey supports both global macros and env macros
- peers.{name}.filters.stripParams supports both macro types
- peers.{name}.filters.setParams supports both macro types
Also renamed validateMetadataForUnknownMacros to validateNestedForUnknownMacros
for reuse across model metadata and peer filters validation.
Benson Wong
75fced579e