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/emoji.go

@@ -0,0 +1,109 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"net/http"
+	"regexp"
+	"sort"
+)
+
+const (
+	EmojiNameMaxLength = 64
+	EmojiSortByName    = "name"
+)
+
+var EmojiPattern = regexp.MustCompile(`:[a-zA-Z0-9_+-]+:`)
+
+type Emoji struct {
+	Id        string `json:"id"`
+	CreateAt  int64  `json:"create_at"`
+	UpdateAt  int64  `json:"update_at"`
+	DeleteAt  int64  `json:"delete_at"`
+	CreatorId string `json:"creator_id"`
+	Name      string `json:"name"`
+}
+
+func (emoji *Emoji) Auditable() map[string]interface{} {
+	return map[string]interface{}{
+		"id":         emoji.Id,
+		"create_at":  emoji.CreateAt,
+		"update_at":  emoji.UpdateAt,
+		"delete_at":  emoji.CreateAt,
+		"creator_id": emoji.CreatorId,
+		"name":       emoji.Name,
+	}
+}
+
+func inSystemEmoji(emojiName string) bool {
+	_, ok := SystemEmojis[emojiName]
+	return ok
+}
+
+func GetSystemEmojiId(emojiName string) (string, bool) {
+	id, found := SystemEmojis[emojiName]
+	return id, found
+}
+
+func makeReverseEmojiMap() map[string][]string {
+	reverseEmojiMap := make(map[string][]string)
+	for key, value := range SystemEmojis {
+		emojiNames := reverseEmojiMap[value]
+		emojiNames = append(emojiNames, key)
+		sort.Strings(emojiNames)
+		reverseEmojiMap[value] = emojiNames
+	}
+
+	return reverseEmojiMap
+}
+
+var reverseSystemEmojisMap = makeReverseEmojiMap()
+
+func GetEmojiNameFromUnicode(unicode string) (emojiName string, count int) {
+	if emojiNames, found := reverseSystemEmojisMap[unicode]; found {
+		return emojiNames[0], len(emojiNames)
+	}
+
+	return "", 0
+}
+
+func (emoji *Emoji) IsValid() *AppError {
+	if !IsValidId(emoji.Id) {
+		return NewAppError("Emoji.IsValid", "model.emoji.id.app_error", nil, "", http.StatusBadRequest)
+	}
+
+	if emoji.CreateAt == 0 {
+		return NewAppError("Emoji.IsValid", "model.emoji.create_at.app_error", nil, "id="+emoji.Id, http.StatusBadRequest)
+	}
+
+	if emoji.UpdateAt == 0 {
+		return NewAppError("Emoji.IsValid", "model.emoji.update_at.app_error", nil, "id="+emoji.Id, http.StatusBadRequest)
+	}
+
+	if len(emoji.CreatorId) > 26 {
+		return NewAppError("Emoji.IsValid", "model.emoji.user_id.app_error", nil, "", http.StatusBadRequest)
+	}
+
+	return IsValidEmojiName(emoji.Name)
+}
+
+func IsValidEmojiName(name string) *AppError {
+	if name == "" || len(name) > EmojiNameMaxLength || !IsValidAlphaNumHyphenUnderscorePlus(name) {
+		return NewAppError("Emoji.IsValid", "model.emoji.name.app_error", nil, "", http.StatusBadRequest)
+	}
+	if inSystemEmoji(name) {
+		return NewAppError("Emoji.IsValid", "model.emoji.system_emoji_name.app_error", nil, "", http.StatusBadRequest)
+	}
+
+	return nil
+}
+
+func (emoji *Emoji) PreSave() {
+	if emoji.Id == "" {
+		emoji.Id = NewId()
+	}
+
+	emoji.CreateAt = GetMillis()
+	emoji.UpdateAt = emoji.CreateAt
+}