* Separated out service layer for trusted apps.

* Improved the type structure a bit to avoid using explicit string literals and to add possibility to return OS specific parts of trusted app object in type safe manner.

* Added support for mapping of trusted app to exception item and back.

* Changed schema to support signer in the API.

* Renamed utils to mapping.

* Exported some types in lists plugin and used them in trusted apps.

* Added tests for mapping.

* Added tests for service.

* Switched deletion to use exceptions for not found case.

* Added resetting of the mocks in service layer tests.

* Added handlers tests.

* Refactored mapping tests to be more granular based on the case.

* Restored lowercasing of hash.

* Added schema tests for signer field.

* Removed the grouped tests (they were split into tests for separate concerns).

* Corrected the tests.

* Lowercased the hashes in the service test.

* Moved the lowercasing to the right location.

* Fixed the tests.

* Added test for lowercasing hash value.

* Introduced OperatingSystem enum instead of current types.

* Removed os list constant in favour of separate lists in places that use it (each place has own needs to the ordering).

* Fixed the missed OperatingSystem enum usage.