Doesn't seem used since it's been broken forever on python 3:
base64.b64encode returns binary data, on which json.dumps chokes.
Still, removing the endpoint on old stables seems a bit brutal so just
fix it.
closesodoo/odoo#56650
X-original-commit: 7fc9bc28986d69184df5a4fdeefbe09e4b39b8f0
Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>