Server side validation missing.

[brett-lempereur]

There needs to be some validation on the server side beyond "it's a valid JSON document so let's store it." At a minimum we should:

• Check that the size of the response is reasonable (<1MB?) before attempting to interpret it.
• Check that none of the identification fields are empty.
• Check that the email address is valid.
• Check that at least one asset has been submitted.
• Check that all assets are not missing required fields.

We should be safe in terms of JSON parsing as the default Python configuration will stick to its conversion table and not perform magic with deserialising objects.