Starts application processes for a shard after its database opens.
A module used as shard_children: {module, :child_specs, args} can implement
validate_child_options!/1. The cluster calls it before starting, so a
configuration error does not leave shards retrying their startup.
Summary
Callbacks
Raises ArgumentError for invalid application settings.
Callbacks
@callback child_specs(Slap.Cluster.Shard.t()) :: [ Supervisor.child_spec() | {module(), term()} ]
@callback validate_child_options!(keyword()) :: :ok
Raises ArgumentError for invalid application settings.