How to generate Google-managed certificates for wildcard hostnames in GCP?

Thanks @James' s answer. I also reference this doc.

I would like to post a concret example for this question in case anyone have the same doubts as me.

Most of the steps could reference to the doc, I would like to point out two steps you need to take care of.

In Create a Google-managed certificate referencing the DNS authorization step, provide your single domain and your wildcard hostname in the --domains options.

gcloud certificate-manager certificates create "my-cert" \
    --domains="example.com,*.example.com" \
    --dns-authorizations=my-dns-auth

In Create a certificate map entry step, create two entries for both single hostname and wildcard hostname.

gcloud certificate-manager maps entries create "my-entry1" \
    --map=my-map \
    --certificates=my-cert \
    --hostname="example.com"

gcloud certificate-manager maps entries create "my-entry2" \
    --map=my-map \
    --certificates=my-cert \
    --hostname="*.example.com"