function getCredentialValue(key) {
        try {
            const fs = SA.nodeModules.fs
            fs.accessSync(key, fs.constants.F_OK)
            return fs.readFileSync(key, {encoding: 'utf8'})
        }
        catch(error) {
            return key
        }
    }
Checks if the provided value is a file, 
if true it returns the file content, 
else returns the key

@param {string} key 
@returns {string}