Create a new action signature

Create a new action signature with a timestamp of 'now'

Create a new action signature with default user and now timestamp

Create a new signature by parsing the given buffer, which is expected to be in the format "Real Name <email> timestamp tzoffset", where timestamp is the number of seconds since the Unix epoch and tzoffset is the timezone offset in hhmm format (note the lack of a colon separator)

Create a copy of an existing signature duplicated.

Free an existing signature