Support global security settings

[rtaycher]

Describe the bug
I realized the openapi standard let's you set a global security/auth setting and that this would cut down a bunch of boilerplate. Sadly when I tried it the generator ignored the global auth and generated non authenticated Clients since each individual operation lacked a local security section

Expected behavior
It should generate matching Authenticated Client for every operation when global security section is set (except for those operations which explicitly override it with a local security section)