Sync/camunda external task client python3 features

[S-Holstein]

Implemented missing features:

• Enable ExternalTask to access config variable of a worker
• Automaticall detect variable types
• Obfuscate passwords in config variable, but should be improved to all kinds of passwords or secrets...
• Allow global variables on task failure

Already implemented:

• Add get_process_instance_history function (

  operaton-external-task-client-python3/operaton/client/engine_client.py

  Line 182 in 730fd73

  def get_process_instance_history(self, process_instance_id):

  )
• Fetch and lock multiple tasks, run a batch function on all tasks (e.g., optimized SQL query for all tasks), and finally complete tasks for all successful executions. (

  operaton-external-task-client-python3/operaton/external_task/external_task_worker.py

  Line 48 in 730fd73

  def fetch_and_execute(self, topic_names, action, process_variables=None, variables=None):

  )
• handle shutdown signal of a worker (finish all running and locked tasks, do not fetch new tasks), example see s1ard-worker (

  operaton-external-task-client-python3/operaton/external_task/external_task_worker.py

  Line 20 in 730fd73

  self.stop_event = stop_event

  )