Add opportunity to start contact tracing from a given date (< 4 weeks ago)

[oliverhummel]

The current practive requires corona.zv to collect contacts of an infected person for a few days prior to the date of the positive PCR test. The system delivers all contacts of the last four weeks so that a lot of manual filtering is necessary.

Hence, the system must be able to do this filtering based on a selected date during the execution of a contact tracing.

Current implementation idea: add a date selection field to the frontend, pre-fill it with a date a week ago and use the selected value to constraint the DB query of the contact tracing to this time period.

[oliverhummel]

Additional idea: it might also be feasible to do the filtering of dates in the frontend only, which would open the opportunity to do this dynamically. This would however, only make sense if a list of mail addresses is available for copying here, the generated excel sheets cannot be adapted in the frontend anymore...