2/
Because most people wouldn't be able to add custom attributes or custom values to most Fediverse software (including Mastodon) —
Most supporting software would probably want to support a "PropertyValue" link in "attachment" field as a fall-back
For example:
"attachment": [
{
"type": "PropertyValue",
"name": "Video Calls (callpub)",
"value": "https://videocalls.example/users/joeblow"
}
But —
...
#ActivityPub #ActivityStreams #AudioCall #Call #FediDev #Fediverse #VideoCall