ExpectedDescriptorIDs returns the list of all expected system descriptor IDs, including those added by completed migrations.

NewManager initializes and returns a new Manager object.

AllMigrations means run all the migrations.

ExcludeMigrationsIncludedInBootstrap means don't run migrations with the includedInBootstrap field set.

SettingsDefaultOverrides documents the effect of several migrations that add an explicit value for a setting, effectively changing the "default value" from what was defined in code.

Manager encapsulates the necessary functionality for handling migrations of data in the cluster.

MigrationManagerTestingKnobs contains testing knobs.

MigrationFilter is used to indicate to EnsureMigrations what to run.