How to automate addition of mandatory shared flow into the proxy bundle

There are several related concepts:

• Shared Flow - a reusable sequence of policies. Think of this as a unit of re-usability for a series of steps. Like a function or subroutine in a 4th generation programming language. A good example is a check-and-fill of a cache. Eg: Load an item from cache; if the cache is empty, then load the item from the external resource and then store it in the cache. This series of steps might take 3 or 4 policies, but it can be considered as one "Step" and would be a good candidate for encapsulation into a shared flow.
• Flow callout - a policy that allows an API proxy to explicitly call out to a shared flow - to invoke the sequence of its policies in order. BTW, a Shared Flow can include a Flow callout policy - one shared flow can call another.
• Flow Hook - a mechanism to enforce IMPLICIT calls to shared flows at specific points during policy execution. FlowHooks are configured per environment.

All of these things are documented.

You are asking about "mandatory shared flow".

There are various ways that I can think of to enforce a "mandatory" shared flow, for varying degress of "enforcement".

1. build your shared flow. configure a FlowHook at the desired point to invoke that shared flow. Now, every proxy deployed to the environment will execute that shared flow.
2. Require your deployments to go through an automated CI/CD build process, and within that process, inject a FlowCallout policy into the API proxy at the desired point.
3. Use an "code generation" or template mechanism (like mvn archetype generate), in which users start with a template of an API Proxy. In the template, insert the call to the desired shared flow. This is obviously something that a user could subvert or change, so it's not really "enforcement". More like "encouragement".