Fix "invalid use of incomplete type ‘std::stringstream'" (#36)
Fix "invalid use of incomplete type ‘std::stringstream'" (#36)

* Fix "invalid use of incomplete type ‘std::stringstream'"

Include <sstream> to fix this issue for gcc7/8 on linux

Same fix as 37ac531413b0b571aca052fce2eb237a056dc4bb but
for new files, I guess

* FIx Moved includes to jwtpp.hh

Co-authored-by: Anton Schmidt <d349fd5bb3708e7508dc486bd2af0e2f2633b781@tsfer.ru>
troian/josepp,atroian/jwtpp