Add privacy policy columns to forge_instances table for assisting with compliance auditing #519

#293 is already working towards creating a new database table for tracking forge instances to use for collection.

This table should allow us to store the following extra info:

• the URL to the forge's privacy policy
• a date the policy was last reviewed for compliance
• A name (or the username) of the person who filled in these two above fields most recently.

this will help create a foundation for surfacing this prompt to check the compliance to admins when adding new instances.