Merge pull request #498 from sylvaindeloux/master

Fixed serialization
Improved doc formatting
Merge pull request #499 from Bladrak/doc

Improved doc formatting
Update creating_a_provider_class.rst

Update type hinting from Media to MediaInterface.
Update creating_a_provider_class.rst
Merge pull request #500 from desarrolla2/patch-1

Update creating_a_provider_class.rst
[documentation] improve Sphinx support
Added POST Gallery API controller
Fixed Gallery validation