IsBadRequest returns true if the given error is a 'bad request' error.

IsTransient returns true if the given error is a 'transient' error.

NewBadRequest returns a 'bad request' error that wraps the given error in order to indicate to the caller that the request was invalid.

NewTransient returns a transient error that wraps the given error in order to indicate to the caller that a retry may resolve the problem, whereas a non-transient (persistent) error will always fail with the same outcome if retried.

ErrContentNotFound is used to indicate that content at a given address could not be found.