* Implemented device macro for GraphQLUnion's
* Updated PR link in CHNAGELOG
* Disabled documentation on enumeration fields
* Disabled skip on fields
* Changed implementation for std::convert::Into since skip is not possible
* Added documentation for GraphQLUnion
* Added tests for GraphQLUnion
* Fixed typos in error messages (as suggested by review)
* Fixed failing documentation example
* Utilized `resolver_code` in `util::GraphQLTypeDefinitionField`.
Simplifies code and provides the idea of using
`util::GraphQLTypeDefinitionField` for different types than objects.
* Removed wrong statement about skip annotation in docs.
Co-authored-by: Christian Legnitto <LegNeato@users.noreply.github.com>
