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

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

server/platform/shared/filestore/filesstore.go

@@ -41,6 +41,10 @@ type FileBackend interface {
 	RemoveDirectory(path string) error
 }
 
+type FileBackendWithLinkGenerator interface {
+	GeneratePublicLink(path string) (string, time.Duration, error)
+}
+
 type FileBackendSettings struct {
 	DriverName                         string
 	Directory                          string
@@ -56,6 +60,7 @@ type FileBackendSettings struct {
 	AmazonS3Trace                      bool
 	SkipVerify                         bool
 	AmazonS3RequestTimeoutMilliseconds int64
+	AmazonS3PresignExpiresSeconds      int64
 }
 
 func NewFileBackendSettingsFromConfig(fileSettings *model.FileSettings, enableComplianceFeature bool, skipVerify bool) FileBackendSettings {
@@ -82,6 +87,31 @@ func NewFileBackendSettingsFromConfig(fileSettings *model.FileSettings, enableCo
 	}
 }
 
+func NewExportFileBackendSettingsFromConfig(fileSettings *model.FileSettings, enableComplianceFeature bool, skipVerify bool) FileBackendSettings {
+	if *fileSettings.ExportDriverName == model.ImageDriverLocal {
+		return FileBackendSettings{
+			DriverName: *fileSettings.ExportDriverName,
+			Directory:  *fileSettings.ExportDirectory,
+		}
+	}
+	return FileBackendSettings{
+		DriverName:                         *fileSettings.ExportDriverName,
+		AmazonS3AccessKeyId:                *fileSettings.ExportAmazonS3AccessKeyId,
+		AmazonS3SecretAccessKey:            *fileSettings.ExportAmazonS3SecretAccessKey,
+		AmazonS3Bucket:                     *fileSettings.ExportAmazonS3Bucket,
+		AmazonS3PathPrefix:                 *fileSettings.ExportAmazonS3PathPrefix,
+		AmazonS3Region:                     *fileSettings.ExportAmazonS3Region,
+		AmazonS3Endpoint:                   *fileSettings.ExportAmazonS3Endpoint,
+		AmazonS3SSL:                        fileSettings.ExportAmazonS3SSL == nil || *fileSettings.AmazonS3SSL,
+		AmazonS3SignV2:                     fileSettings.ExportAmazonS3SignV2 != nil && *fileSettings.AmazonS3SignV2,
+		AmazonS3SSE:                        fileSettings.ExportAmazonS3SSE != nil && *fileSettings.AmazonS3SSE && enableComplianceFeature,
+		AmazonS3Trace:                      fileSettings.ExportAmazonS3Trace != nil && *fileSettings.AmazonS3Trace,
+		AmazonS3RequestTimeoutMilliseconds: *fileSettings.ExportAmazonS3RequestTimeoutMilliseconds,
+		AmazonS3PresignExpiresSeconds:      *fileSettings.ExportAmazonS3PresignExpiresSeconds,
+		SkipVerify:                         skipVerify,
+	}
+}
+
 func (settings *FileBackendSettings) CheckMandatoryS3Fields() error {
 	if settings.AmazonS3Bucket == "" {
 		return errors.New("missing s3 bucket settings")