A head context pinned to fiber#storage

I suggest adding a routine head context that should be initialized with new fiber and it should be pinned into new fiber#storage. The profit: such context is convenient enough to use among few classes and it exists only while fiber works and then it can disappear with fiber.

The idea based on fiber#storage

The production case: we have the special market platform with good number of vendors, about several thousands, they need an integrations with another platforms to get data or to upload some output there. To implement it we have to repeat among classes the same variables, arguments and code such as vendor object, their feature settings, repositories scoped by vendor, their configurations to access an external resources, etc.

Another simplified case (just as illustration) with similar problem in Rails: when variables defined in controller are available from several templates and partials.

The possible implementation: