correct Maybe usage
Wrap content setting in Response:

Instead of the solution in faaa685158e9432cc2ea3714e26a7df0e72824b7,
we use an "around" modifier to simply wrap the "content" method
to decide whether to serialize or not.

This removes the need for "set_content", "get_content", and having
both an attribute "content" and a method "content" (which itself is
either a setter or getter as well).
Fix deserialzier test:

The only change we're not sure about (but had to do) was to remove
the Encode::decode() call when returning parameters from the POST
request that had GET parameters with UTF8.

For some reason it was already decoded.
count :/
rewrite test, sort of, to fix the errors
more fixes
Merge branch 'fix/fix'