A processor to transform the client credentials to the key that
ObjectStoreClientStore will use to store clients
in the underlying object store.
If the key formatter implementation uses the client secret for key generation:
1. client removal operation must also receive the secret.
2. Custom client security provider is not supported.
To register a custom key formatter:
1. Custom Key Formatter must be added to the registry.
2. The ObjectStore used for client storage must provide a pre-loaded client entry under the USE_CUSTOM_KEY_FORMATTER
key. Said client should have as clientId the name under which the formatter was registered in the registry.