Function write_settings 

pub async fn write_settings(
    conn: &mut PgConnection,
    app_config: &ApplicationConfiguration,
    settings: &CourseSettingsSnapshot,
    live: &CourseSettingsSnapshot,
    can_change_chatbot: bool,
    embeddings: &TextEmbeddings,
) -> ModelResult<Course>

Writes the course settings of the snapshot without recording history: the course row in one write, and the audiences that differ from live, the current settings. Embeddings of the changed name, description and audiences come from embeddings where it has them. Errors with PreconditionFailed if the snapshot is of another course, or if it changes can_add_chatbot and can_change_chatbot is false.