Update vendor (#1297)

vendor/github.com/mattermost/mattermost-server/v5/model/channel_sidebar.go

@@ -6,6 +6,7 @@ package model
 import (
 	"encoding/json"
 	"io"
+	"regexp"
 )
 
 type SidebarCategoryType string
@@ -109,3 +110,15 @@ func (o OrderedSidebarCategories) ToJson() []byte {
 		return b
 	}
 }
+
+var categoryIdPattern = regexp.MustCompile("(favorites|channels|direct_messages)_[a-z0-9]{26}_[a-z0-9]{26}")
+
+func IsValidCategoryId(s string) bool {
+	// Category IDs can either be regular IDs
+	if IsValidId(s) {
+		return true
+	}
+
+	// Or default categories can follow the pattern {type}_{userID}_{teamID}
+	return categoryIdPattern.MatchString(s)
+}