Hiku

* 3c28d22 Merge pull request 144 from evo-company/export-scalars-in-sdl
* effb309 export scalars in sdl

* 299cd89 Merge pull request 141 from evo-company/fix-enum-as-arg-and-scalar-default
* bd4468f Fix custom scalar introspection defaultValue. Fix enum opt validation

* 1c8bffe Merge pull request 140 from evo-company/fix-scalars-for-options
* 26e2f46 Fix custom scalar validations for options

* 685d98d Merge pull request 138 from evo-company/add-extensions-factory
* 4f89aef add ExtensionFactory, forbid to pass Extension instances to Endpoint due to thread-safety
* 466c75f Merge pull request 136 from evo-company/add-tests-for-endpoint-with-context
* 4016792 add tests for endpoint with CustomContext

* 6d9f666 Merge pull request 135 from evo-company/fix-changelog-generation
* 7d777d1 fix changelog generation