Indicate ready for deletion as kafka event

[andreasfrisch]

❗ Suggestion only

💡 Idea:
By sending an event when capabilities are ready to be deleted, other processes can react to this event too, automating deletion substeps

🌟 Changes:

• Background job checking pending deletion capabilities now emits an event for all capabilities which have been pending for 7 days.
• Creates a handler, reacting to the new event, marking capabilities as deleted.
• Reuses existing topic cloudengineering.selfservice.capabilities
• Added tests for the this new kafka flow
• Added an additional capability state ongoing deletion

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