fix: remove $unsharedHeaders and add $defaultOptions
fix: remove $unsharedHeaders and add $defaultOptions

$defaultOptions is options passed in the constructor.
They are applied for all requests.
All request headers are cleared after sending request,
and $defaultOptions are set again.

samsonasik/CodeIgniter4,lonnieezell/CodeIgniter4,samsonasik/CodeIgniter4,kenjis/CodeIgniter4,bcit-ci/CodeIgniter4,kenjis/CodeIgniter4,lonnieezell/CodeIgniter4,bcit-ci/CodeIgniter4,samsonasik/CodeIgniter4,lonnieezell/CodeIgniter4,kenjis/CodeIgniter4,bcit-ci/CodeIgniter4,lonnieezell/CodeIgniter4,kenjis/CodeIgniter4,lonnieezell/CodeIgniter4,bcit-ci/CodeIgniter4,lonnieezell/CodeIgniter4,samsonasik/CodeIgniter4,samsonasik/CodeIgniter4,kenjis/CodeIgniter4,samsonasik/CodeIgniter4,bcit-ci/CodeIgniter4