v12.10.0

• po / gettext: entries that differ only by their msgctxt stay apart. The
  key holds msgid and msgctxt joined by U+0004 (as gettext does in .mo
  files), and download writes it back as msgctxt. Until now they merged
  into one key, which kept one variant and dropped the others.
  po_i18next / gettext_i18next are unchanged (_ context, i18next's
  convention).
• sync with po / gettext sends an entry's msgctxt as the context of the
  keys it adds, so translators and the AI see it; existing keys keep their
  context, migrate sends none.
• Upgrading with po / gettext files that use msgctxt: the first sync
  adds those entries as new keys; where a file has no plain entry for that
  text, the old merged key is removed (unless --skip-delete true), together
  with its translations. format and migrate produce the new keys as well.
• update gettext-converter to 1.4.1 (plural entries keep their msgctxt).