DATAREST-1012 - added test to reproduce issue DATAREST-1012, fix Domain…

[stefanreichert]

Hey guys,

I implemented a Unit Test to reproduce the error observed (see DomainObjectReaderTest) as well as a fix for the DomainObjectReader. Feedback is welcome, accepting the pull request even more ;)

Thanks for your great work, best regards,
Stefan

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[odrotbohm]

Would you mind squashing the commits and coming up with a commit message that actually describes the effect of the changes you made. From looking at the code I can see some grouping of collection items by type that definitely needs explanation.

Also, see more general comments on the ticket.

[stefanreichert]

The change basically sticks to the existing implementation but considers the runtime type of the object to be merged to avoid the 'incompatibility' error. I'll squash the two commits and add a decent message. Thanks for your feedback!

[stefanreichert]

OK, this PR is outdated so I'll withdraw it...