Availability history

How this works: each injury or availability spell can contain several dated updates. Games missed are linked to the spell automatically where possible. A fitness-building spell can also be recorded without counting the player as injured. Post-injury fitness updates may stay linked to the original injury spell after the injury itself has closed. A recorded first match back is shown when entered. An inferred return fixture is shown only when an explicit recovery/Available update closes the spell; closing a spell because the player's situation became unclear or the player began an outgoing loan does not count as a recovery.