PLT-3143 Added serverside code for custom Emoji (#3311)

* Added model objects for emoji

* Added database tables for emoji

* Added settings for custom emoji

* Added serverside APIs and unit tests for custom emoji

* Added additional validation to catch duplicate emoji names earlier on

* Added additional validation to prevent users from adding emoji as another user

model/emoji.go

@@ -0,0 +1,95 @@
+// Copyright (c) 2016 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package model
+
+import (
+	"encoding/json"
+	"io"
+)
+
+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) IsValid() *AppError {
+	if len(emoji.Id) != 26 {
+		return NewLocAppError("Emoji.IsValid", "model.emoji.id.app_error", nil, "")
+	}
+
+	if emoji.CreateAt == 0 {
+		return NewLocAppError("Emoji.IsValid", "model.emoji.create_at.app_error", nil, "id="+emoji.Id)
+	}
+
+	if emoji.UpdateAt == 0 {
+		return NewLocAppError("Emoji.IsValid", "model.emoji.update_at.app_error", nil, "id="+emoji.Id)
+	}
+
+	if len(emoji.CreatorId) != 26 {
+		return NewLocAppError("Emoji.IsValid", "model.emoji.user_id.app_error", nil, "")
+	}
+
+	if len(emoji.Name) == 0 || len(emoji.Name) > 64 {
+		return NewLocAppError("Emoji.IsValid", "model.emoji.name.app_error", nil, "")
+	}
+
+	return nil
+}
+
+func (emoji *Emoji) PreSave() {
+	if emoji.Id == "" {
+		emoji.Id = NewId()
+	}
+
+	emoji.CreateAt = GetMillis()
+	emoji.UpdateAt = emoji.CreateAt
+}
+
+func (emoji *Emoji) PreUpdate() {
+	emoji.UpdateAt = GetMillis()
+}
+
+func (emoji *Emoji) ToJson() string {
+	b, err := json.Marshal(emoji)
+	if err != nil {
+		return ""
+	} else {
+		return string(b)
+	}
+}
+
+func EmojiFromJson(data io.Reader) *Emoji {
+	decoder := json.NewDecoder(data)
+	var emoji Emoji
+	err := decoder.Decode(&emoji)
+	if err == nil {
+		return &emoji
+	} else {
+		return nil
+	}
+}
+
+func EmojiListToJson(emojiList []*Emoji) string {
+	b, err := json.Marshal(emojiList)
+	if err != nil {
+		return ""
+	} else {
+		return string(b)
+	}
+}
+
+func EmojiListFromJson(data io.Reader) []*Emoji {
+	decoder := json.NewDecoder(data)
+	var emojiList []*Emoji
+	err := decoder.Decode(&emojiList)
+	if err == nil {
+		return emojiList
+	} else {
+		return nil
+	}
+}