get resume id from server

[coderlxn]

[olesalscheider]

LGTM.

[jlaine]

IQ parsing / serialization is trivial to unit test, so do it :)

[jlaine]

@coderlxn can we please have a unit test for this so we can merge it?

[jlaine]

@lnjX I'm not sure I understand what this does anymore, ideas?

[lnjX]

@jlaine The session id needs to be parsed to be able to resume the session (using previd in <resume/>) after a possible connection loss.

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See https://xmpp.org/extensions/xep-0198.html#resumption

[coderlxn]

@jlaine What kind of unit test should I add for this pull request? Sorry, I'm not familiar with the progress of pull request.

[lnjX]

Unfortunately there's no test class for stream management, yet, but you could base on this test basically. It were also nice to have this new test class in a new commit.