function chkParamFname(params) {
    const res = { statusMessage: '', status: 0, }
    const fname = params.fname

    // We have to have an fname (file name) to work with
    if ( fname === undefined ) {
        res.statusMessage = 'file name not provided'
        res.status = 500
        return res
    }
    // Blank file name probably means no files available so we will ignore
    if ( fname === '' ) {
        res.statusMessage = 'file name cannot be blank'
        res.status = 500
        return res
    }
    // fname must not exceed 255 characters
    if ( fname.length > 255 ) {
        res.statusMessage = `file name is too long. Max 255 characters: ${params.fname}`
        res.status = 500
        return res
    }
    // fname cannot contain .. to prevent escaping sub-folder structure
    if ( fname.includes('..') ) {
        res.statusMessage = `file name may not contain "..": ${params.fname}`
        res.status = 500
        return res
    }

    return res
}
Validate fname (filename) query parameter
@param {object} params The GET (res.query) or POST (res.body) parameters
@param {string} params.fname The uibuilder url to check
@returns {{statusMessage: string, status: number}} Status message