[ECS] [request]: Ability to define Operators in ECS

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**Tell us about your request**
What do you want us to build? Customers who run stateful applications or databases, or want to customize the interaction with ECS do not have a way to do that. Would a capability in ECS to easily register custom resources and custom controllers with lifecycle hooks enable a new set of use cases? The controller could run as another ECS service.

If you have use cases that can benefit from this functionality, we would like to learn more.

**Which service(s) is this request for?**
This could be for ECS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.

**Are you currently working around this issue?**
How are you currently solving this problem?

Customers today work around this lack of customization by listening to events and running custom code to integrate with any third party applications they use

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