v0.7.0

Removed

• Breaking: admin.Register and admin.Stage. The consumer declares the service on its
  coordinator at the stage its own stage table names:
  lc.Add(lifecycle.Service{Name: "schema", Stage: <stage>, Start: svc.Start, Check: svc}).

Changed

• The go-core requirement is v0.5.0; the integer overrides use its config.SetFromEnv.
• Breaking: database.ErrConnectionFailed is sqlate.ErrConnectionFailed, one sentinel for
  a failure to reach the database, whether the pool or a session raised it.
• Breaking: Service.Force refuses a version that is not one of the named set's migrations
  with admin.ErrValidation, before any I/O. It returned the migrator's
  migrate.ErrVersionNotFound before.
• Breaking: Service.Ready reports the schema alone: every set's history clean and current.
  A seeder whose statements do not prepare fails Verify and Start but no longer clears it,
  and Start sets it once, when every step has passed.
• Service.Reset with an empty state resets to the configured Options.Seed set, as
  Service.Seed does. It refused with admin.ErrSeedDisabled before.
• Service.States returns a copy of the seeder's list.
• The admin.Seeder contract states that Seed stays idempotent when replicas seed at once.
• Each package comment lists the package's API, and each contract is stated once, on its symbol.

Added

• admin.ErrConflict wraps every refusal the schema's state causes (dirty, pending, a history
  its set does not carry, a migration with no down, a set order the migrator forbids), with the
  migrate sentinel kept in the chain.
• database.Config.Finalized reports whether Finalize has filled every field New reads; the
  providers check it.
• database.DB.ConnTimeout returns the configured conn_timeout.
• Once Start has succeeded, a not-ready Service.Ready verifies the schema itself, one probe
  at a time, at most once per five seconds, and bounded by the pool's conn_timeout, so a
  replica whose schema is corrected out of band returns to rotation. A probe's clean finding
  yields to any operation that determined the schema while it read.

Fixed

• An admin operation that failed without determining the schema's state, such as a cancelled
  GET of the schema's status or a lost connection, cleared Service.Ready, taking the replica
  out of rotation until another operation found the schema current. Ready now changes only on a
  determined state.
• A misspelled Options.Seed failed Start only after it had applied pending migrations; it
  now fails before Start reads the schema.