fix: Remove footer from reactions on the receiver side (#4780)

Reactions do not have footer since 6d2ac30. However, mailing lists still add the footer to the
messages, and receiver interpreted words as a reaction.

src/reaction.rs

@@ -431,6 +431,32 @@ Content-Disposition: reaction\n\
         assert_eq!(bob_reaction.emojis(), vec!["👍"]);
         assert_eq!(bob_reaction.as_str(), "👍");
 
+        // Alice receives reaction to her message from Bob with a footer.
+        receive_imf(
+            &alice,
+            "To: alice@example.org\n\
+From: bob@example.net\n\
+Date: Today, 29 February 2021 00:00:10 -800\n\
+Message-ID: 56790@example.net\n\
+In-Reply-To: 12345@example.org\n\
+Subject: Meeting\n\
+Mime-Version: 1.0 (1.0)\n\
+Content-Type: text/plain; charset=utf-8\n\
+Content-Disposition: reaction\n\
+\n\
+😀\n\
+\n\
+--\n\
+_______________________________________________\n\
+Here's my footer -- bob@example.net"
+                .as_bytes(),
+            false,
+        )
+        .await?;
+
+        let reactions = get_msg_reactions(&alice, msg.id).await?;
+        assert_eq!(reactions.to_string(), "😀1");
+
         Ok(())
     }