Function serialize_user_provider_option 

pub fn serialize_user_provider_option<S>(
    value: &Option<SecretString>,
    serializer: S,
) -> Result<S::Ok, S::Error>
where
    S: Serializer,

Serializes a user_provider option, exposing only known file-based forms.

The option is held as a [SecretString] so Debug and the default serializer never print it. This serializer exposes the value only to keep provider names and file paths visible for those forms in configuration dumps such as the /config endpoint.