Creates a new secret.
The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).
The callback for this method is defined as:
'err' is the error that occurred. If there was no error, then 'err' is 'null'.
'err' has 2 properties which hold detailed information:
The value passed for SecretName must consist solely of alphanumeric characters, hyphens (-), and underscores (_); and may be up to 255 characters in length.
If there are any items in the Label* properties, they will be applied to the newly-created secret. Secrets may have up to 64 labels.
Note that this method makes two requests: the first one creates the empty secret itself (which is just a container for secret versions), and the second one creates an initial secret version with the actual secret data (as if CreateVersion had been called). The Id of the initial secret version is always 1.