By adding `force=True` to request.get_json() the mime type is ignore. If the data is not valid json the method will return a `BadRequestError` we catch that and throw our own error with a clear error message "Invalid JSON supplied in POST data".
If the json is valid return the json data or an empty dict if None is passed in.
This PR improves the error messages if the json is invalid, previously, the error message was "None object type" message which is not very helpful.
If you’re trying to show what a Notify email will look like in your
caseworking system all the API gives you at the moment is raw markdown
(with the placeholders replaced).
This isn’t that useful if your caseworkers have no idea what markdown
is. If we also give teams the HTML then they can embed this in their
systems, and the people using those systems will be able to see how
headings, bulleted lists, etc. look.
