[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>

webapp/platform/types/src/config.ts

@@ -200,6 +200,7 @@ export type ClientConfig = {
     AllowPersistentNotificationsForGuests: string;
     DelayChannelAutocomplete: 'true' | 'false';
     ServiceEnvironment: string;
+    UniqueEmojiReactionLimitPerPost: string;
 };
 
 export type License = {
@@ -378,6 +379,7 @@ export type ServiceSettings = {
     PersistentNotificationIntervalMinutes: number;
     PersistentNotificationMaxCount: number;
     PersistentNotificationMaxRecipients: number;
+    UniqueEmojiReactionLimitPerPost: number;
     RefreshPostStatsRunTime: string;
 };