String line to encode.
An encoded Base64 string.
{
    immutable password = "harbl snarbl 12345";
    immutable encoded = encode64(password);
    assert((encoded == "aGFyYmwgc25hcmJsIDEyMzQ1"), encoded);
}
{
    immutable string password;
    immutable encoded = encode64(password);
    assert(!encoded.length, encoded);
}
Base64-encodes a string.
Merely wraps std.base64.Base64.encode and std.string.representation into one function that will work with strings.