Container for all (if there are any) keys between Prefix and the next occurrence of the string
specified by a delimiter. CommonPrefixes lists keys that act like subdirectories in the directory
specified by Prefix. For example, if the prefix is notes/ and the delimiter is a slash (/) as in
notes/summer/july, the common prefix is notes/summer/.
Container for all (if there are any) keys between Prefix and the next occurrence of the string specified by a delimiter. CommonPrefixes lists keys that act like subdirectories in the directory specified by Prefix. For example, if the prefix is notes/ and the delimiter is a slash (/) as in notes/summer/july, the common prefix is notes/summer/.