OASFactory.INSTANCE ignores the resolver set about microprofile-open-api

[arthurdm]

@leochr / @mrglavas - can you please take a look into this one?

[leochr]

The OASFactory follows the same static resolver pattern as of ConfigProvider from MP Config.

We also posted in the google forum about the static resolver pattern and were told that it's fine/reasonable to expect that there is only one implementation of resolver within a vendor's environment and it be set at the beginning (vendor's responsibility). OASFactoryResolver.setInstance is to be used by OSGi environment while service loader pattern is not supported. Vendor should set the factory resolver before the factory class is loaded.

@Emily-Jiang your thoughts about the static resolver?

We decided the OASFactory to be static so it's easy for end users to invoke the static createObject method. e.g. OASFactory.createObject(Info.class).title("Airlines")

[arthurdm]

Solved by merge #85