v8.0 module release (#22975)

https://mattermost.atlassian.net/browse/MM-52079

```release-note
We upgrade the module version to 8.0. The new module path is github.com/mattermost-server/server/v8.
```


Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

server/model/reaction_test.go

@@ -0,0 +1,188 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestReactionIsValid(t *testing.T) {
+	tests := []struct {
+		// reaction
+		reaction Reaction
+		// error message to print
+		errMsg string
+		// should there be an error
+		shouldErr bool
+	}{
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: "emoji",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "",
+			shouldErr: false,
+		},
+		{
+			reaction: Reaction{
+				UserId:    "",
+				PostId:    NewId(),
+				EmojiName: "emoji",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "user id should be invalid",
+			shouldErr: true,
+		},
+		{
+			reaction: Reaction{
+				UserId:    "1234garbage",
+				PostId:    NewId(),
+				EmojiName: "emoji",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "user id should be invalid",
+			shouldErr: true,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    "",
+				EmojiName: "emoji",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "post id should be invalid",
+			shouldErr: true,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    "1234garbage",
+				EmojiName: "emoji",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "post id should be invalid",
+			shouldErr: true,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: strings.Repeat("a", 64),
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "",
+			shouldErr: false,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: "emoji-",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "",
+			shouldErr: false,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: "emoji_",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "",
+			shouldErr: false,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: "+1",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "",
+			shouldErr: false,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: "emoji:",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "",
+			shouldErr: true,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: "",
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "emoji name should be invalid",
+			shouldErr: true,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: strings.Repeat("a", 65),
+				CreateAt:  GetMillis(),
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "emoji name should be invalid",
+			shouldErr: true,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: "emoji",
+				CreateAt:  0,
+				UpdateAt:  GetMillis(),
+			},
+			errMsg:    "create at should be invalid",
+			shouldErr: true,
+		},
+		{
+			reaction: Reaction{
+				UserId:    NewId(),
+				PostId:    NewId(),
+				EmojiName: "emoji",
+				CreateAt:  GetMillis(),
+				UpdateAt:  0,
+			},
+			errMsg:    "update at should be invalid",
+			shouldErr: true,
+		},
+	}
+
+	for _, test := range tests {
+		appErr := test.reaction.IsValid()
+		if test.shouldErr {
+			// there should be an error here
+			require.NotNil(t, appErr, test.errMsg)
+		} else {
+			// err should be nil here
+			require.Nil(t, appErr, test.errMsg)
+		}
+	}
+}