Some methods are provided to allow you to add validation errors to the collection
manually and alter the state of the Errors hash.

errors[:base] = msg
Adds an error message related to the overall object state itself and not the value of any
particular attribute. Make your error messages complete sentences, because Rails does
not do any additional processing of them to make them readable.

errors[:attribute] = msg
Adds an error message related to a particular attribute. The message should be a sentence
fragment that reads naturally when prepended with the capitalized name of the attribute.

As you might expect, the clear method clears the Errors collection.