Cache api keys in memorystore

[steveoh]

We're getting charged for some firestore reads since it's going above the free tier. It's not much, like less than a quarter, but it's not necessary.

Every request to the api reads from firestore to get the api key details. I'm thinking we can cache the api key details in redis with a time to live setting to remove some repeated pressure on firestore.

The only issue is that a key is paused or deleted and the cache needs to be cleared.

I'm thinking a dotnet background service can check for pub/sub topics on a schedule to check for self service actions to keys that the api needs to react to.