>>> isBase64Url "PDw_Pj4=" True
>>> isBase64Url "PDw_Pj4" True
>>> isBase64Url "PDw_Pj" False
>>> isValidBase64Url "PDw_Pj4=" True
>>> isValidBase64Url "PDw_Pj" True
>>> isValidBase64Url "%" False
>>> isBase64Url "PDw_Pj4=" True
>>> isBase64Url "PDw_Pj4" True
>>> isBase64Url "PDw_Pj" False
>>> isValidBase64Url "PDw_Pj4=" True
>>> isValidBase64Url "PDw_Pj" True
>>> isValidBase64Url "%" False
>>> isBase64Url "PDw_Pj4=" True
>>> isBase64Url "PDw_Pj4" True
>>> isBase64Url "PDw_Pj" False
>>> isValidBase64Url "PDw_Pj4=" True
>>> isValidBase64Url "PDw_Pj" True
>>> isValidBase64Url "%" False
>>> isBase64Url "PDw_Pj4=" True
>>> isBase64Url "PDw_Pj4" True
>>> isBase64Url "PDw_Pj" False
>>> isValidBase64Url "PDw_Pj4=" True
>>> isValidBase64Url "PDw_Pj" True
>>> isValidBase64Url "%" False
>>> isBase64Url "PDw_Pj4=" True
>>> isBase64Url "PDw_Pj4" True
>>> isBase64Url "PDw_Pj" False
>>> isBase64Url "PDw_Pj4=" True
>>> isBase64Url "PDw_Pj4" True
>>> isBase64Url "PDw_Pj" False
>>> isValidBase64Url "PDw_Pj4=" True
>>> isValidBase64Url "PDw_Pj" True
>>> isValidBase64Url "%" False