[MM-53454] Add export file settings + slash command for public link (#23915)

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

server/cmd/mmctl/commands/export.go

@@ -40,6 +40,13 @@ var ExportDownloadCmd = &cobra.Command{
 	RunE: withClient(exportDownloadCmdF),
 }
 
+var ExportGeneratePresignedURLCmd = &cobra.Command{
+	Use:   "generate-presigned-url [exportname]",
+	Short: "Generate a presigned url for an export file. This is helpful when an export is big and might have trouble downloading from the Mattermost server.",
+	Args:  cobra.ExactArgs(1),
+	RunE:  withClient(exportGeneratePresignedURLCmdF),
+}
+
 var ExportDeleteCmd = &cobra.Command{
 	Use:     "delete [exportname]",
 	Aliases: []string{"rm"},
@@ -115,6 +122,7 @@ func init() {
 		ExportListCmd,
 		ExportDeleteCmd,
 		ExportDownloadCmd,
+		ExportGeneratePresignedURLCmd,
 		ExportJobCmd,
 	)
 	RootCmd.AddCommand(ExportCmd)
@@ -171,6 +179,22 @@ func exportDeleteCmdF(c client.Client, command *cobra.Command, args []string) er
 	return nil
 }
 
+func exportGeneratePresignedURLCmdF(c client.Client, command *cobra.Command, args []string) error {
+	name := args[0]
+
+	presignedURL, _, err := c.GeneratePresignedURL(context.TODO(), name)
+	if err != nil {
+		return fmt.Errorf("failed to generate export link: %w", err)
+	}
+
+	printer.PrintT("Export link: {{.Link}}\nExpiration: {{.Expiration}}", map[string]interface{}{
+		"Link":       presignedURL.URL,
+		"Expiration": presignedURL.Expiration.String(),
+	})
+
+	return nil
+}
+
 func exportDownloadCmdF(c client.Client, command *cobra.Command, args []string) error {
 	var path string
 	name := args[0]