[feature] implement substring body fetch

Current twisted implementation correctly parses partial fetches using
substrings by use of angle brackets (see section 6.4.5 of imap rfc), but
no use is made of the requested substring in the spew_body method.

this commit minimally implements conformance to the substring request,
although further boundary checks should be made (ie, checking whether
the starting octet is beyond the end of the text).

Resolves: #6841
Releases: 0.4.0

0 files changed, 0 insertions, 0 deletions