stringprep_xmpp_nodeprep converts value as lowercase

[hamzaozturk]

libidn-framework/Framework/NSString+IDN.m

Line 6 in fc2700c

+ (nullable NSString *)idn_prepNode:(NSString *)node

if(stringprep_xmpp_nodeprep(buf, sizeof(buf)) != 0) return nil;

This function causes value to be lowercase.

XMPPJID(string: "B9C897C3-1826-48EF-8BF1-6F957B741855@example.com")

if i init XMPPJID like above, it returns as

"b9c897c3-1826-48ef-8bf1-6f957b741855@example.com"

Is there a special reason that it converts node value as lowercase?