Add additional struct to Custom hostname

[SanchosPancho]

Add additional struct to Custom hostname

Description

This change allow to get from api information about SSL certificate for custom hostname. Information like
Issuer, SerialNumber, Signature, ExpiresOn, IssuedOn, Fingerprint.

It's very useful in case when you need to monitoring certificate expiration date or certificate fingerprint for security reason and etc.

Has your change been tested?

Yes, I've test expiration days left for my certificate.

Screenshots (if appropriate):

Types of changes

What sort of change does your code introduce/modify?

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• This change is using publicly documented (api.cloudflare.com or developers.cloudflare.com) and stable APIs.