Constant PREFETCH_FLAGS

const PREFETCH_FLAGS: &str = "(UID INTERNALDATE RFC822.SIZE BODY.PEEK[HEADER.FIELDS (\
                              MESSAGE-ID \
                              DATE \
                              X-MICROSOFT-ORIGINAL-MESSAGE-ID \
                              FROM \
                              IN-REPLY-TO REFERENCES \
                              CHAT-VERSION \
                              AUTO-SUBMITTED \
                              AUTOCRYPT-SETUP-MESSAGE\
                              )])";

Prefetch:

• Message-ID to check if we already have the message.
• In-Reply-To and References to check if message is a reply to chat message.
• Chat-Version to check if a message is a chat message
• Autocrypt-Setup-Message to check if a message is an autocrypt setup message, not necessarily sent by Delta Chat.