On May 1, 2018, GitHub announced that GitHub Pages now gain support for HTTPS. It states that you're all set for this feature if you use CNAME or ALIAS records; or, updated DNS with new IP addresses for A records.
Then, you may Enforce HTTPS:
However, my Enforce HTTPS option is disabled, stating:
Unavailable for your site because a certificate has not yet been issued for your domain
Is this an automated process that takes GitHub time to complete; or, an action I am supposed to perform? From their Troubleshooting Custom Domains page, it states:
If you've chosen to use Certification Authority Authorization (CAA) records, at least one CAA record must exist with the value letsencrypt.org for your GitHub Pages site to be accessible over HTTPS. For more information, see "Certificate Authority Authorization (CAA)" in the Let's Encrypt documentation.
Does this mean I am supposed to create a new CAA DNS record?
What does this record need to contain for Let's Encrypt services used by GitHub? Or, do I use my own domain in this record, as in:
0 issue caa.mydomain.tld