Added middleware to modify porecess details response and replace the callback...

Added middleware to modify porecess details response and replace the callback result with a URl, and Implemented get callback result by step-id endpoint.

docs/source/apidocs/index.rst

+API Reference
+=============
+
+This page contains auto-generated API reference documentation [#f1]_.
+
+.. toctree::
+   :titlesonly:
+
+   gso/gso
+
+.. [#f1] Created with `sphinx-autodoc2 <https://github.com/chrisjsewell/sphinx-autodoc2>`_