Add extra test

Merge branch 'master' of gitlab.switch.ch:memoriav/memobase-2020/libraries/mapper-service-configuration

Proxy type

Adds an internal proxyType value to the digital object.
The default value is `proxydirect`.
The field can be a direct mapped field, a constant or a prefixed field.

See merge request memoriav/memobase-2020/libraries/mapper-service-configuration!1

First case is an empty person name.

Fix tests.

Remove serialization support code in mappers. This was a failed attempt deserialization is now just done after merging in Kafka.

Replace local InvalidMappingException class with the same class defined in the service utility library.

Update tests to reflect changes.

Add some pseudo tests to agent mapper.