MUC: Don't default component admins to being room owners
This change has various technical and social benefits. If ownership of a MUC
is really needed, it can be gained using the 'Set affiliation' ad-hoc command
or prosodyctl shell.
Example client incompatibility with the old behaviour:
- https://github.com/monal-im/Monal/issues/1085
# server MUST keep a record of the complete presence stanza comprising the subscription request (#689)
[Client] Alice
jid: pars-a@localhost
password: password
[Client] Bob
jid: pars-b@localhost
password: password
[Client] Bob's phone
jid: pars-b@localhost/phone
password: password
---------
Alice connects
Alice sends:
<presence to="${Bob's JID}" type="subscribe">
<preauth xmlns="urn:xmpp:pars:0" token="1tMFqYDdKhfe2pwp" />
</presence>
Alice disconnects
Bob connects
Bob sends:
<presence/>
Bob receives:
<presence from="${Bob's full JID}"/>
Bob receives:
<presence from="${Alice's JID}" type="subscribe">
<preauth xmlns="urn:xmpp:pars:0" token="1tMFqYDdKhfe2pwp" />
</presence>
Bob disconnects
# Works if they reconnect too
Bob's phone connects
Bob's phone sends:
<presence/>
Bob's phone receives:
<presence from="${Bob's phone's full JID}"/>
Bob's phone receives:
<presence from="${Alice's JID}" type="subscribe">
<preauth xmlns="urn:xmpp:pars:0" token="1tMFqYDdKhfe2pwp" />
</presence>
Bob's phone disconnects