Swap out iframely (#1706)

Swap out iframely (#1706)

* Replace Iframely. Fixes #1681

* Add post_link_tags to nginx

* Adding post_link_tags route

* Cleaning up post_link_tags

* Changing PostLink to SiteMetadata, adding it to the API.

* Fixing issue when local has no openssl certs.

* Fixing an issue with pictrs errors

* Revert "Fixing issue when local has no openssl certs."

This reverts commit dbf7d1b1ee03846e5ef7b7156e618424f1150e1d.

* Add ca-certs to dockerfile for volume mount.

* Cleaning up fetch_pictrs request

* Changing to fetch_site_data