Add optional support for TTL (Time to Live) for state stores

[wanton7]

In what area(s)?

/area runtime

Describe the feature

If I have example a Redis state store that I want to use as cache, having support for TTL when writing a state would be very beneficial. State stores that don't support TTL could just ignore TTL.

[denis111]

+1. Would be very useful for storing session tokens (like allow (for logged in) or deny (for logged-out) users) even for things like stateless jwt tokens for additional security.

[yaron2]

State API calls take in an optional metadata per request.

Does something like the following seem reasonable? (HTTP example)

/v1.0/state/redis

[
  {
     "key": "key1",
     "value: "myVal",
     "metadata": {
         "ttl": "1d"
     }
  }
]

[denis111]

@yaron2 I guess it would be fine.
Right now we use Spring Boot's redis client and it has @TimeToLive annotation wich you put on long property in the class you want to save in redis, maybe something similar could be made in dapr's java sdk, if not then it's not a problem setting metadata property manually.

[berndverst]

We'll use ttlInSeconds in metadata, just like for PubSub

[yaron2]

Changing to P2.