Function embed_changed_metadata 

async fn embed_changed_metadata(
    conn: &mut PgConnection,
    app_config: &ApplicationConfiguration,
    course_id: Uuid,
    edit: &impl Fn(&CourseSettingsSnapshot) -> CourseSettingsSnapshot,
    prerequisites: &[EditCoursePrerequisite],
) -> ModelResult<TextEmbeddings>

Embeds the settings texts that edit of the live settings and saving prerequisites would add or change.