Fix a bug in isValidAuxChar where valid characters '.' and ':' were
incorrectly included in the banned charset. This issue affected the
validation of auxiliary fields in the nodes.conf file used by Valkey in
cluster mode, particularly when handling IPv4 and IPv6 addresses. The
code now correctly allows '.' and ':' as valid characters, ensuring
proper handling of these fields. Comments were added to clarify the use
of the banned charset.
Related to #736
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Signed-off-by: Ping Xie <pingxie@google.com>
ad0ede302c