Add Workflow Transition plugin files and configuration for automated task handling

[Fr3shDev]

Pull Request resolves issue #4 .

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

Adds a new Joomla Scheduler task plugin plg_task_workflowtransition that fires automated workflow transitions for items whose scheduled deadline has passed.

• Registers a workflow.automation task type with com_scheduler
• On each run, joins workflow_automation_schedule with workflow_transitions and workflow_transition_automation to find all (item, rule) pairs where next_transition_at <= NOW() and the rule is not currently locked
• Groups results by rule and locks each rule via locked_until before processing to prevent concurrent scheduler instances from double-firing the same transition
• Sets the application state flag workflow.triggered_by = 'automation' before calling Workflow::executeTransition() so plg_workflow_automation records the correct trigger source in workflow_automation_schedule
• Uses try/finally to guarantee the lock is released and the flag is reset even if a transition throws
  This plugin is the execution engine of the automated workflow feature. It depends on plg_workflow_automation (introduced in PR #3) to populate workflow_automation_schedule and keep next_transition_at up to date.

Testing Instructions

1. Apply PR #3 (plg_workflow_automation) first if not already merged
2. Drop the plugins/task/workflowtransition/ directory into your Joomla installation
3. Go to System → Discover, discover and install "Workflow - Automation Task", then enable it
4. Ensure at least one row exists in #__workflow_transition_automation with published = 1 and a valid interval_value/interval_unit
5. Manually transition a content item through a workflow stage that has an automation rule — this causes plg_workflow_automation to write a row to #__workflow_automation_schedule with a computed next_transition_at
6. Either wait for next_transition_at to pass or manually update the row: UPDATE #__workflow_automation_schedule SET next_transition_at = NOW() WHERE id = X;
7. Go to System → Scheduled Tasks, create a new task of type "Workflow Automation", save, and click Run
8. Re-query #__workflow_automation_schedule and verify:

• The item's stage_id changed to the target stage
• triggered_by = 'automation'
• next_transition_at reflects the deadline for the new stage (or NULL if no rule applies)

9. Query #__workflow_transition_automation and verify locked_until is NULL (lock released)

Actual result BEFORE applying this Pull Request

No automated mechanism exists to fire workflow transitions on a schedule. All transitions require manual user action in the Joomla admin.

Expected result AFTER applying this Pull Request

Items in a workflow stage with a configured automation rule are automatically transitioned to the target stage when their scheduled deadline passes. The transition is recorded with triggered_by = 'automation' in #__workflow_automation_schedule, distinguishing automated transitions from manual ones.

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed