The field definition. Type:

public FieldItemBase::__construct(DataDefinitionInterface $definition,

public static FieldItemDataDefinition::c

public FieldStorageConfig::getCardinality()

public static BaseFieldOverride::createFromBaseFieldDef

public FieldStorageDef

The maximum length of the field name, in characters. For fields created through Field UI, this includes the 'field_' prefix.

public FieldItemBase::storageSettingsForm(array &$form, FormStateInterface

public FieldConfigInterface::setDefaultValueCallback($callback)

public static FieldConfigBase::createFromItemType($item_type)