Support for vendor specific media types

[zersaegen]

This issue has already been reported here and several times on stackoverflow but still there is no answer on how to add vendor specific media types like application/vnd.com.company.entity+json so they get rendered as HAL.

After looking into the project I would have expected two ways to add custom media types:

1. Override the media types in Jackson2ModuleRegisteringBeanPostProcessor where the message converter and the object mapper are set up. I don't know if this is even possible but I did not find an obvious way to do so, so I assume and hope this is not the way one should go.
2. Extend HypermediaType but as this is a enum, I don't see a way to do this either.

Both ways really seem to make it hard to add custom media types, and I can't imagine/I don't hope the supposed ways in the mentioned issue or on stackoverflow are the way to go.

Funny enough, I even gave an answer to the stackoverflow question I mentioned above myself (here) but still one year later there is no way to support this absolutey basic Hateoas feature. How is a media type driven library supposed to work if it does not support media types? I don't want to be harsh and I really appreciate all the effort put in this project, but I just don't get it. Currently it feels more like a spring-hal project.

Stackoverflow:
1
2

Other related issues:
#333
#263
#262
#134
#87
#37

[gregturn]

Related to #518

[gregturn]

Resolved via #833.