MM-23489 Fix poor Unicode handling in display names (#14214)

Filter blacklisted Unicode characters from:

user: first name, last name, nickname, bot description, username
team: name, display name, description, company name
channel: name, display name

api4/channel_test.go

@@ -317,6 +317,64 @@ func TestPatchChannel(t *testing.T) {
 	CheckForbiddenStatus(t, resp)
 }
 
+func TestChannelUnicodeNames(t *testing.T) {
+	th := Setup(t).InitBasic()
+	defer th.TearDown()
+	Client := th.Client
+	team := th.BasicTeam
+
+	t.Run("create channel unicode", func(t *testing.T) {
+		channel := &model.Channel{
+			Name:        "\u206cenglish\u206dchannel",
+			DisplayName: "The \u206cEnglish\u206d Channel",
+			Type:        model.CHANNEL_OPEN,
+			TeamId:      team.Id}
+
+		rchannel, resp := Client.CreateChannel(channel)
+		CheckNoError(t, resp)
+		CheckCreatedStatus(t, resp)
+
+		require.Equal(t, "englishchannel", rchannel.Name, "bad unicode should be filtered from name")
+		require.Equal(t, "The English Channel", rchannel.DisplayName, "bad unicode should be filtered from display name")
+	})
+
+	t.Run("update channel unicode", func(t *testing.T) {
+		channel := &model.Channel{
+			DisplayName: "Test API Name",
+			Name:        GenerateTestChannelName(),
+			Type:        model.CHANNEL_OPEN,
+			TeamId:      team.Id,
+		}
+		channel, _ = Client.CreateChannel(channel)
+
+		channel.Name = "\u206ahistorychannel"
+		channel.DisplayName = "UFO's and \ufff9stuff\ufffb."
+
+		newChannel, resp := Client.UpdateChannel(channel)
+		CheckNoError(t, resp)
+
+		require.Equal(t, "historychannel", newChannel.Name, "bad unicode should be filtered from name")
+		require.Equal(t, "UFO's and stuff.", newChannel.DisplayName, "bad unicode should be filtered from display name")
+	})
+
+	t.Run("patch channel unicode", func(t *testing.T) {
+		patch := &model.ChannelPatch{
+			Name:        new(string),
+			DisplayName: new(string),
+			Header:      new(string),
+			Purpose:     new(string),
+		}
+		*patch.Name = "\u206ecommunitychannel\u206f"
+		*patch.DisplayName = "Natalie Tran's \ufffcAwesome Channel"
+
+		channel, resp := Client.PatchChannel(th.BasicChannel.Id, patch)
+		CheckNoError(t, resp)
+
+		require.Equal(t, "communitychannel", channel.Name, "bad unicode should be filtered from name")
+		require.Equal(t, "Natalie Tran's Awesome Channel", channel.DisplayName, "bad unicode should be filtered from display name")
+	})
+}
+
 func TestCreateDirectChannel(t *testing.T) {
 	th := Setup(t).InitBasic()
 	defer th.TearDown()