Add StartDate to limit contacts search result

[maxones25]

Related Issue

• Add opportunity to start contact tracing from a given date (< 4 weeks ago) #292

Proposed Changes

• a date field was added to the search form and to make the search in the database start from a certain date
• the contact list is displayed filtered by the search. the start date is also displayed on the results page

Additional Info

Checklist

• Is the code formatted correctly?
• Unnecessary comments removed?
• Printout statements removed?
• If you made backend changes: Did all tests pass? Do you need to adjust some tests or write new ones?
• If you made frontend changes: Did you test the UI on different devices/ browsers (Firefox, Chrome, Safari, different smartphone sizes)
• Is your code easy to understand or do you need to insert some comments?
• Explain the issue for the reviewer and your steps to solve the issue => makes it a lot more easy for the reviewer
• Label your pull request (frontend/ backend/ testing/ styling/ sql/...)
• Is the open source message included at the very beginning of every source code file?
• Are all imports organized, i.e. are the imports up to date and have all package imports been removed?

[maxones25]

I have added some tests for contact tracing