Support Expect-CT header

[daurnimator]

• Draft Spec
• https://scotthelme.co.uk/a-new-security-header-expect-ct/
• Chrome feature available since chrome 61

Client side support

• [x] Support for Expect-CT header in lpeg_patterns (Tracking issue: https://github.com/daurnimator/lpeg_patterns/issues/11)
• [ ] Track known expect-ct hosts
• [ ] Support report-uri
  • This requires json library
  • May want to turn off by default for privacy?

  • UAs SHOULD limit the rate at which they send reports. For example, it is unnecessary to send the same report to the same "report-uri" more than once.

• [ ] Come up with a CT Policy
  • Google's
  • Need to include default log providers? See https://www.certificate-transparency.org/known-logs

Server side support

• Probably need https://github.com/wahern/luaossl/issues/105