The labels -> content link table should include (possibly using ConfluenceEntityObject properties:

• Who labeled the content (lastModifierName?)
• When the label was applied (lastModificationDate?)
• Space key to which the label was applied (may be null)

Rather than have lots of different classes of labels, the label table should store prefix and labelname (so my:favourite has prefix 'my') and we do label type lookups by distinguishing on prefix.