support for x-ms-file-request-intent header

when using an OAuth token, the `x-ms-file-request-intent` should be set to `backup`:

see https://learn.microsoft.com/en-us/rest/api/storageservices/set-file-properties#common-request-headers
> Required if Authorization header specifies an OAuth token. Acceptable value is backup. This header specifies that the Microsoft.Storage/storageAccounts/fileServices/readFileBackupSemantics/action or Microsoft.Storage/storageAccounts/fileServices/writeFileBackupSemantics/action should be granted if they're included in the RBAC policy assigned to the identity that is authorized using the Authorization header. Available for version 2022-11-02 and later.