Appdata developer ID
<developer id="mterry.name">
<name translatable="no">Michael Terry</name>
</developer>
https://gitlab.gnome.org/World/deja-dup/-/blob/main/data/app.metainfo.xml.in?ref_type=heads#L67-69
Appstream decided to use reverse DNS for developer IDs.
The element should have a id property, containing a unique ID to identify the component developer / development team. It is recommended to use a reverse-DNS name, like org.gnome or io.github.ximion, or a Fediverse handle (like @user@example.org) as ID to achieve a higher chance of uniqueness.
More information: https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-developer