API changes for skipped actions: patch actions and status_message

This patch implements the changes in the API required for the
skipped action blueprint. It includes:

- New field `status_message` is visible in API get calls for Audits,
  ActionPlans and Audits.
- New Patch call is added to `/actions/{action_id}` which allows to
  manually move actions in PENDING state to SKIPPED for ActionPlans
  which have not been started.
- A new API microversion 1.5 is added for these changes.

It also adds requried tests and documentation.

Implements: blueprint add-skip-actions

Assisted-By: Cursor (claude-4-sonnet)

Change-Id: I71fb9af76085e5941a7fd3e9e4c89d6f3a3ada47
Signed-off-by: Alfredo Moralejo <amoralej@redhat.com>

doc/source/image_src/plantuml/action_state_machine.txt

@@ -0,0 +1,23 @@
+@startuml
+
+skinparam ArrowColor DarkRed
+skinparam StateBorderColor DarkRed
+skinparam StateBackgroundColor LightYellow
+skinparam Shadowing true
+
+[*] --> PENDING: The Watcher Planner\ncreates the Action
+PENDING --> SKIPPED: The Action detects skipping condition\n in pre_condition or was\n skipped by cloud Admin.
+PENDING --> FAILED: The Action fails unexpectedly\n in pre_condition.
+PENDING --> ONGOING: The Watcher Applier starts executing/n the action.
+ONGOING --> FAILED: Something failed while executing\nthe Action in the Watcher Applier
+ONGOING --> SUCCEEDED: The Watcher Applier executed\nthe Action successfully
+FAILED --> DELETED : Administrator removes\nAction Plan
+SUCCEEDED --> DELETED : Administrator removes\n theAction
+ONGOING --> CANCELLED : The Action was cancelled\n as part of an Action Plan cancellation.
+PENDING --> CANCELLED : The Action was cancelled\n as part of an Action Plan cancellation.
+CANCELLED --> DELETED
+FAILED --> DELETED
+SKIPPED --> DELETED
+DELETED --> [*]
+
+@enduml