Pleroma, Akkoma, and other servers do not follow the Mastodon spec
for the 'uri' attribute which specifies that it contains the domain
name of the instance. Instead, they return a complete URI.
As a workaround, we now detect this situation and parse out the
domain from the URI when necessary. This fixes issue #347.
Thanks to @laleanor for their patch and @rjp for ideas on how to
make it work with GotoSocial and other servers
The instance domain can be different from their base url, for example
the instance at https://social.vivaldi.net uses the vivaldi.net domain,
sans 'social'.
This commit requires the user to provide the base url of the instance,
instead of domain name. The domain is then fetched from the server.
fixes#217
