Is it possible to install SSL public and private certificates through the Gateway API?

Is it possible to install new SSL public and private certificates through the Gateway API to either use in new API definitions or to rotate soon to be expired certificates without having to upload them through other means to the filesystem?

The following is mentioned in the docs:

Dynamically setting SSL certificates for custom domains

If you include certificateID or certificate path to API definition certificates field, Gateway will dynamically load this ceritficate for your custom domain, so you will not need to restart the process. You can do it from Dashboard UI too, in custom domain section.

But I was not able to find any additional details around this.

Sorry for a delayed response. If you need an urgent professional support, we usually recommend to reach out to our account managers.

About your question - I might misunderstood you, but you can use the endpoint /api/certs as explained here

You are right that you can upload certificates directly to API definition, like on example above

Using this feature, you do not need to maintain files, and once you update API certificates, Gateway will automatically apply it without restarting the process.

Hope it makes sense!