encodeBase64(user, pass) {
        return Buffer.from(`${user || ""}:${pass || ""}`).toString("base64");
    }
Encode user and password to Base64 encoding
for HTTP "basic" auth, as per RFC-7617
@param {string|null} user - The username (nullable if not changed by a user)
@param {string|null} pass - The password (nullable if not changed by a user)
@returns {string} Encoded Base64 string