Add Dynamic Prefix To Cache Key

[jorgechacons]

Adding hook to pass a function with access to request context to return a dynamic prefix for each key.
This feature allows the developers to pass identifiers to the keys, so it makes it searchable for redis-cli or memcached that use key-based searches.

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[glasser]

Would it make more sense to let you override cacheKeyString instead? (Note that this would also subsume the functionality of extraCacheKeyData which could be deprecated.)

[jorgechacons]

@glasser That sounds good too, however at least for our case extraCacheKeyData is not used, because that will be hashed so it is not searchable for redis

I added a new hook, to be able to share the requestContext to extract data like operationName, etc

[glasser]

I think I might not have been clear here. I feel like the concept of "dynamic prefix" is too specific. Both "dynamic prefix" and "extra cache key data" are ways to influence the calculation of the cache key, and it would make more sense to just let you define a "calculate the cache key" hook instead of providing more ad hoc tweaks to the existing one. Happy to review and merge a PR that does this more general change (which would also let us deprecate extraCacheKeyData and drop it in AS4) rather than this more specific one.

[glasser]

We released a similar feature (generateCacheKey) in AS v3.10.0. Thanks for the inspiration!