cmd: Add Support for Piping Input to Start a DAG

[yohamta]

Enable Dagu to accept input via standard input (stdin) when starting a workflow. This feature will enhance usability by allowing users to pass parameters dynamically using shell pipelines.

Example Usage:

echo "parameter" | dagu start workflow_name  

[ghansham]

Just a quick solution, calling curl post request can do the trick. And the better part is it can work from remote system as well. Refer to:

https://dagu.readthedocs.io/en/latest/rest.html#submit-dag-action-post-api-v1-dags-name

For example

curl -H 'Content-Type: application/json' -d '{"Action": "start", "params": "parameter_values_string"}' -X POST http://IP:port/api/v1/dags/dagname

where params_string can be either passed as command line argument to the curl wrapper shell script.

We can have a generalized script with dagname, params_string, action and IP address in it.
Another advantage is we need to specify only dagname. Not the full path.