Implement logic to set/monitor current CWA user with regards to certificates. (#3509)

...ificate/common/certificate/CertificatePersonIdentifier.kt

...arnapp/covidcertificate/person/core/PersonCertificates.kt

...ovidcertificate/person/core/PersonCertificatesProvider.kt

...ovidcertificate/person/core/PersonCertificatesSettings.kt

...idcertificate/test/core/storage/TestCertificateStorage.kt

...-App/src/main/java/de/rki/coronawarnapp/util/DataReset.kt

...certificate/person/core/PersonCertificatesProviderTest.kt

...dcertificate/person/core/PersonCertificatesStorageTest.kt

.../src/test/java/de/rki/coronawarnapp/util/DataResetTest.kt