[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

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

server/config/client.go

@@ -140,6 +140,7 @@ func GenerateClientConfig(c *model.Config, telemetryID string, license *model.Li
 	props["PersistentNotificationMaxRecipients"] = strconv.FormatInt(int64(*c.ServiceSettings.PersistentNotificationMaxRecipients), 10)
 	props["AllowSyncedDrafts"] = strconv.FormatBool(*c.ServiceSettings.AllowSyncedDrafts)
 	props["DelayChannelAutocomplete"] = strconv.FormatBool(*c.ExperimentalSettings.DelayChannelAutocomplete)
+	props["UniqueEmojiReactionLimitPerPost"] = strconv.FormatInt(int64(*c.ServiceSettings.UniqueEmojiReactionLimitPerPost), 10)
 
 	if license != nil {
 		props["ExperimentalEnableAuthenticationTransfer"] = strconv.FormatBool(*c.ServiceSettings.ExperimentalEnableAuthenticationTransfer)