Project: mesos
Issue MESOS-4183: Move operator<< definitions to .cpp files and include <iosfwd> in .hpp where possible.
We often include complex headers like {{}} in ".hpp" files to define {{operator<<()}} inline (e.g. "mesos/authorizer/authorizer.hpp"). Instead, we can move definitions to corresponding ".cpp" files and replace stream headers with {{iosfwd}}, for example, this is partially done for {{URI}} in "mesos/uri/uri.hpp".
Story points: 3