Movim is incorrectly generating XEP-0339 <source> element

[goffi-contrib]

During a call where Movim is the initiator, it convert the following SDP ssrc attributes for the video stream:

a=ssrc:134219770 cname:{8c7db19c-9153-48f2-b62b-c1042bc76bbd}
a=ssrc:1998259287 cname:{8c7db19c-9153-48f2-b62b-c1042bc76bbd}

to following XEP-0339 elements:

<source xmlns="urn:xmpp:jingle:apps:rtp:ssma:0" ssrc="134219770">
  <parameter value="{8c7db19c-9153-48f2-b62b-c1042bc76bbd}" name="cname"/>
  <parameter value="{8c7db19c-9153-48f2-b62b-c1042bc76bbd}" name="cname"/>
</source>

Incorrectly merging the parameters and discarding the second source. This is incorrect, and it should be instead:

<source xmlns="urn:xmpp:jingle:apps:rtp:ssma:0" ssrc="134219770">
  <parameter value="{8c7db19c-9153-48f2-b62b-c1042bc76bbd}" name="cname"/>
</source>
<source xmlns="urn:xmpp:jingle:apps:rtp:ssma:0" ssrc="1998259287">
  <parameter value="{8c7db19c-9153-48f2-b62b-c1042bc76bbd}" name="cname"/>
</source>

Accidentally, this make the call work with Conversations which incorrectly refuse multiple sources, but this is a bug a ignore the retransmission source, which degrades the call quality.

Tested with Movim v0.21rc7

Note: there is a bug in Conversations preventing the call to work with multiple sources: https://codeberg.org/iNPUTmice/Conversations/issues/58