Required. An opaque token that uniquely identifies the account among all the platform's accounts. This string may contain at most 64 non-whitespace ASCII characters, but otherwise has no predefined structure. However, it is expected to be a platform-specific identifier for the user creating the account, so that only a single account can be created for any given user. This field must not contain any information that is recognizable as personally identifiable information. e.g. it should not be an email address or login name. Once an account has been created, a second attempt to create an account using the same creation_request_id will result in an ALREADY_EXISTS error.