Rebuild channel index (#26080)

* WIP

* Added rebuild channels index functionality

* Added rough logic to send message to all sysadmins

* WIP

* WIP

* WIP

* Cleanup

* i18n fix

* reading through all pages of system admins

* Fixed webapp style

* i18n fix

* Added help text

* i18n fix

* i18n update

* Updated system console button action

* Updated snapshots

* some cleanup

* Updated snapshot

* Update server/channels/app/server.go

Co-authored-by: Daniel Espino García <larkox@gmail.com>

* fixed typo

* Refactoring to improve readibility

* moved index check to API later during config update

* Added some docs

* Updated get system bot

---------

Co-authored-by: Daniel Espino García <larkox@gmail.com>

server/channels/api4/config.go

@@ -167,6 +167,15 @@ func updateConfig(c *Context, w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
+	// if ES autocomplete was enabled, we need to make sure that index has been checked.
+	// we need to stop enabling ES autocomplete otherwise.
+	if !*appCfg.ElasticsearchSettings.EnableAutocomplete && *cfg.ElasticsearchSettings.EnableAutocomplete {
+		if !c.App.SearchEngine().ElasticsearchEngine.IsAutocompletionEnabled() {
+			c.Err = model.NewAppError("updateConfig", "api.config.update.elasticsearch.autocomplete_cannot_be_enabled_error", nil, "", http.StatusBadRequest)
+			return
+		}
+	}
+
 	c.App.HandleMessageExportConfig(cfg, appCfg)
 
 	if appErr := cfg.IsValid(); appErr != nil {

server/channels/api4/elasticsearch.go

@@ -71,7 +71,8 @@ func purgeElasticsearchIndexes(c *Context, w http.ResponseWriter, r *http.Reques
 		return
 	}
 
-	if err := c.App.PurgeElasticsearchIndexes(c.AppContext); err != nil {
+	specifiedIndexesQuery := r.URL.Query()["index"]
+	if err := c.App.PurgeElasticsearchIndexes(c.AppContext, specifiedIndexesQuery); err != nil {
 		c.Err = err
 		return
 	}