Function push_log_with_retry 

pub async fn push_log_with_retry(
    client: &impl HttpClient,
    config: &EnvConfig,
    log: &BetterStackLogSchema,
    retry_config: &RetryConfig,
) -> Result<Option<Value>, LogtailError>

Pushes a log with automatic retry on transient failures.

Uses exponential backoff with optional jitter. Only retries on errors where is_retryable() returns true (5xx HTTP errors and network errors).