Description of problem:
Many of the models that are part of Katello/SystemEngine do not do integrity checks.
For example

Take ActivationKey
# => ActivationKey(id: integer, name: string, description: string, organization_id: integer, environment_id: integer, system_template_id: integer, created_at: datetime, updated_at: datetime, user_id: integer)

Now there is nothing to check for the fact that the environment_id/system_template_id belong to the same organization as organization_id when we save the model. In the UI we only show the valid values to be selected but  there is nothing preventing the user from sending wrong environment ids. 

This kind of audit probably needs to happen with many other models.