Provide additional, neutral value "control period = not specified" for CET-Attribute "documented period"

ARCM: Control Execution

For each Control Execution, a period is calculated from the Control Execution Task Definition's attribute "documented period" and "offset" (German: "Länge der dokumentierten Periode", "offset"). This "documented period" is shown in ARCM's control execution as a space of time from date A to date B.

eg.: Documented Period = 2023/01/01 - 2023/01/31

eg.: (German version) Dokumentierter Zeitraum = 01.01.2023 - 31.01.2023

In practice, there are Control Executions which do not relate to a specific period, but indeed they relate to the as-is-status of the controlled data at the dated of Control Execution. Therefore, an additional value is necessary für the CET-Definition of attribute "documented period" (German: "Länge der dokumentierten Periode"), and, as a consquence, there should not follow a calculation of a period für the task in ARCM, but in ARCM it should show "documented period = status as per control date" or similar Text (not date/time).

See attached screenshots (available in German only).