EmojiReactValidator: fix emoji qualification

Tries fully-qualifying emoji when receiving them, by adding the emoji
variation sequence to the received reaction emoji.

This issue arises when other instance software, such as Misskey, tries
reacting with emoji that have unqualified or minimally qualified
variants, like a red heart. Pleroma only accepts fully qualified emoji
in emoji reactions, and refused those emoji. Now, Pleroma will attempt
to properly qualify them first, and reject them if checks still fail.

This commit contains changes to tests proposed by lanodan.

Co-authored-by: Haelwenn <contact+git.pleroma.social@hacktivis.me>

test/fixtures/emoji-reaction-unqualified.json

@@ -0,0 +1,30 @@
+{
+  "type": "EmojiReact",
+  "signature": {
+    "type": "RsaSignature2017",
+    "signatureValue": "fdxMfQSMwbC6wP6sh6neS/vM5879K67yQkHTbiT5Npr5wAac0y6+o3Ij+41tN3rL6wfuGTosSBTHOtta6R4GCOOhCaCSLMZKypnp1VltCzLDoyrZELnYQIC8gpUXVmIycZbREk22qWUe/w7DAFaKK4UscBlHDzeDVcA0K3Se5Sluqi9/Zh+ldAnEzj/rSEPDjrtvf5wGNf3fHxbKSRKFt90JvKK6hS+vxKUhlRFDf6/SMETw+EhwJSNW4d10yMUakqUWsFv4Acq5LW7l+HpYMvlYY1FZhNde1+uonnCyuQDyvzkff8zwtEJmAXC4RivO/VVLa17SmqheJZfI8oluVg==",
+    "creator": "http://mastodon.example.org/users/admin#main-key",
+    "created": "2018-02-17T18:57:49Z"
+  },
+  "object": "http://localtesting.pleroma.lol/objects/eb92579d-3417-42a8-8652-2492c2d4f454",
+  "content": "❤",
+  "nickname": "lain",
+  "id": "http://mastodon.example.org/users/admin#reactions/2",
+  "actor": "http://mastodon.example.org/users/admin",
+  "@context": [
+    "https://www.w3.org/ns/activitystreams",
+    "https://w3id.org/security/v1",
+    {
+      "toot": "http://joinmastodon.org/ns#",
+      "sensitive": "as:sensitive",
+      "ostatus": "http://ostatus.org#",
+      "movedTo": "as:movedTo",
+      "manuallyApprovesFollowers": "as:manuallyApprovesFollowers",
+      "inReplyToAtomUri": "ostatus:inReplyToAtomUri",
+      "conversation": "ostatus:conversation",
+      "atomUri": "ostatus:atomUri",
+      "Hashtag": "as:Hashtag",
+      "Emoji": "toot:Emoji"
+    }
+  ]
+}

test/pleroma/web/activity_pub/transmogrifier/emoji_react_handling_test.exs

@@ -37,6 +37,32 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier.EmojiReactHandlingTest do
     assert match?([["👌", _]], object.data["reactions"])
   end
 
+  test "it works for incoming unqualified emoji reactions" do
+    user = insert(:user)
+    other_user = insert(:user, local: false)
+    {:ok, activity} = CommonAPI.post(user, %{status: "hello"})
+
+    data =
+      File.read!("test/fixtures/emoji-reaction-unqualified.json")
+      |> Jason.decode!()
+      |> Map.put("object", activity.data["object"])
+      |> Map.put("actor", other_user.ap_id)
+
+    {:ok, %Activity{data: data, local: false}} = Transmogrifier.handle_incoming(data)
+
+    assert data["actor"] == other_user.ap_id
+    assert data["type"] == "EmojiReact"
+    assert data["id"] == "http://mastodon.example.org/users/admin#reactions/2"
+    assert data["object"] == activity.data["object"]
+    # heart emoji with added emoji variation sequence
+    assert data["content"] == "❤\uFE0F"
+
+    object = Object.get_by_ap_id(data["object"])
+
+    assert object.data["reaction_count"] == 1
+    assert match?([["❤\uFE0F", _]], object.data["reactions"])
+  end
+
   test "it reject invalid emoji reactions" do
     user = insert(:user)
     other_user = insert(:user, local: false)