Improve data validation and consistency

[Glutexo]

Currently the ORM doesn’t check data consistency very thoroughly. It’s possible to manually (not through the API) to create a host that then causes errors when further manipulated. An example can be that the facts field doesn’t default to an empty dictionary on safe etc.

It would be good to take some measures that would make the data more consistent and the app then durable:

• Check the data validity and consistency on save to the database. Do not limit the validation checks only to API requests.
• Set some reasonable default values in a unified ways, e.g. that the facts and system_profile_facts store "{}" instead of "null".

In general, the application is not very friendly to scripting, ad-hoc usages or debugging. Any non-API scripts then become a possibly deadly tool that can botch the database if the developer doesn’t remember all necessary constrains.