[MM-55143] Disallow reacting with an emoji that does not exist, limit the total number of unique reactions per post (#25331)

* [MM-55143] Disallow reacting with an emoji that does not exist

* WIP for server limit on emoji reactions

* WIP

* Implement default limit of 25 unique emoji reactions

* Add modal for reaction limit

* Fix test

* PR feedback

* Fix i18n

* Update admin string

* Merge'd

* Fixing some issues, check limits correctly based on other users reactions

* Fix typos

* Fix lint/test

* Add tests, fix other tests

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/model/config.go

@@ -100,17 +100,19 @@ const (
 
 	SitenameMaxLength = 30
 
-	ServiceSettingsDefaultSiteURL          = "http://localhost:8065"
-	ServiceSettingsDefaultTLSCertFile      = ""
-	ServiceSettingsDefaultTLSKeyFile       = ""
-	ServiceSettingsDefaultReadTimeout      = 300
-	ServiceSettingsDefaultWriteTimeout     = 300
-	ServiceSettingsDefaultIdleTimeout      = 60
-	ServiceSettingsDefaultMaxLoginAttempts = 10
-	ServiceSettingsDefaultAllowCorsFrom    = ""
-	ServiceSettingsDefaultListenAndAddress = ":8065"
-	ServiceSettingsDefaultGiphySdkKeyTest  = "s0glxvzVg9azvPipKxcPLpXV0q1x1fVP"
-	ServiceSettingsDefaultDeveloperFlags   = ""
+	ServiceSettingsDefaultSiteURL                = "http://localhost:8065"
+	ServiceSettingsDefaultTLSCertFile            = ""
+	ServiceSettingsDefaultTLSKeyFile             = ""
+	ServiceSettingsDefaultReadTimeout            = 300
+	ServiceSettingsDefaultWriteTimeout           = 300
+	ServiceSettingsDefaultIdleTimeout            = 60
+	ServiceSettingsDefaultMaxLoginAttempts       = 10
+	ServiceSettingsDefaultAllowCorsFrom          = ""
+	ServiceSettingsDefaultListenAndAddress       = ":8065"
+	ServiceSettingsDefaultGiphySdkKeyTest        = "s0glxvzVg9azvPipKxcPLpXV0q1x1fVP"
+	ServiceSettingsDefaultDeveloperFlags         = ""
+	ServiceSettingsDefaultUniqueReactionsPerPost = 50
+	ServiceSettingsMaxUniqueReactionsPerPost     = 500
 
 	TeamSettingsDefaultSiteName              = "Mattermost"
 	TeamSettingsDefaultMaxUsersPerTeam       = 50
@@ -394,6 +396,7 @@ type ServiceSettings struct {
 	EnableCustomGroups                                *bool   `access:"site_users_and_teams"`
 	SelfHostedPurchase                                *bool   `access:"write_restrictable,cloud_restrictable"`
 	AllowSyncedDrafts                                 *bool   `access:"site_posts"`
+	UniqueEmojiReactionLimitPerPost                   *int    `access:"site_posts"`
 	RefreshPostStatsRunTime                           *string `access:"site_users_and_teams"`
 }
 
@@ -886,6 +889,14 @@ func (s *ServiceSettings) SetDefaults(isUpdate bool) {
 		s.SelfHostedPurchase = NewBool(true)
 	}
 
+	if s.UniqueEmojiReactionLimitPerPost == nil {
+		s.UniqueEmojiReactionLimitPerPost = NewInt(ServiceSettingsDefaultUniqueReactionsPerPost)
+	}
+
+	if *s.UniqueEmojiReactionLimitPerPost > ServiceSettingsMaxUniqueReactionsPerPost {
+		s.UniqueEmojiReactionLimitPerPost = NewInt(ServiceSettingsMaxUniqueReactionsPerPost)
+	}
+
 	if s.RefreshPostStatsRunTime == nil {
 		s.RefreshPostStatsRunTime = NewString("00:00")
 	}