Allow different declarations for process

[shavounet]

Description

Today it's only possible to declare process through YAML. We should find a way to allow easily (with custom code) :

• database stored process : allowing an admin user to create db entities that can be converted into process / transformers
  • maybe it can only be a cookbook
• PHP declarations : allow a quick & functional syntax for process that are not meant to be called in CLI
  • example idea, with some specific functions, and generic functions :

$processBuilder->fromInput()
    ->readFile('csv', $readOptions)                          // hypothetical FileReaderTask, see #78
    ->filter(function($item) {return test($item);})          // hypothetical CallbackFilterTask, maybe linked to #96 
    ->transform(['transformer_code' => $transformerOptions]) // TransformerTask call
    ->pipe($taskService, $taskOptions)                       // generic call
    ->writeFile('csv', $writeOptions);                       // hypothetical FileWriterTask, see #78
$process = $processBuilder->build();

$processManager->execute($process);

Requirements

• Documentation updates
  • Reference
  • Cookbooks
  • Changelog
• Unit tests