Add new test environment TESTER-MOCK + clean up (DEV, EXPOSUREAPP-6138) (#2744)

* Add new test environment TESTER-MOCK + clean up.

* kLint, fun for the whole family.

* Make naming consistent

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>
Co-authored-by: Lukas Lechner <lukas.lechner@sap.com>
Co-authored-by: Lukas Lechner <office@lukaslechner.com>