Deprecate HPKP security header

[jiheon-dev]

Related #4261

Expected Behavior

Since the HPKP HeaderSupport has been deprecated by the browsers in order to support Expect-CT security header, we should deprecate its DSL.

Current Behavior

Spring Security project supports Public-Key-Pins header.

Reference

https://scotthelme.co.uk/hpkp-is-no-more/
https://scotthelme.co.uk/a-new-security-header-expect-ct/

[marcusdacoregio]

Thanks for bringing this up @jiheon-dev.

Since we already have #4261 to add the support for the Expect-CT header, we may transform this issue to deprecate the HPKP header.

Can we change the title to Deprecate HPKP security header, and change the description to add context about this change?

[jiheon-dev]

Yes, I already changed issue title. If you have something to change about my issue context, you can change it anytime.

Thanks for reply my issue @marcusdacoregio