* MM-11272 Added app.PreparePostForClient
* MM-11272 Added app.PreparePostListForClient
* MM-11272 Added EmojiStore.GetMultipleByName
* MM-11272 Added emojis to PreparePostForClient
* MM-11272 Added unit tests for getting reaction counts
* MM-11272 Added unit tests for TestPreparePostForClient
* MM-11272 Added emojis from reactions to Post.Emojis
* MM-11272 Always update post.UpdateAt when reactions change to bust cache
* Fixed merge conflicts
* Moved post metadata-related code into its own file
* Update store mocks
* Fixed typo
* Add missing license headers
* Updated post metadata tests when custom emojis are disabled
* Fix unreliable unit tests
* Fix inconsistent casing in SQL statements
* Fix blank line
* Invalidate store cache after making changes
* Clear post cache synchronously with reactions
* Emoji validation fails if name exists in system emojis
* Use hashmap instead of array to improve performance
* Changed utils/StringInMap to emoji/isSystemEmoji
* Load system emojis from model/emoji.json
* Added emoji.json from webapp
* Load system emojis from emoji_data.go instead of emoji.json
* Run `gofmt -w model/emoji_data.go`
* 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