Token based authentication integration with core extension

[ggivo]

Provide a way for lettuce clients to use token-based authentication.
TOKENs come with a TTL. After a Redis client authenticates with a TOKEN, if they didn't renew their authentication we need to evict (close) them. The suggested approach is to leverage the existing CredentialsProvider and add support for streaming credentials to handle token refresh scenarios. Each time a new token is received connection is reauthenticated.

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[atakavci]

i can anticipate what BaseRedisAuthenticationHandler holds but lets see the actual impl before moving further.

[atakavci]

TokenBasedRedisCredentialsProvider looks nice and clean overall, and does most of the job as i understand. Only thing i got around is that i believe it would do auth twice with the same initial token;
one with a call to

 public Mono<RedisCredentials> resolveCredentials() {
 ... 

and the other with a call to

public Flux<RedisCredentials> credentials() {
...

[ggivo]

Yes, It will do it twice.
I was thinking to skip first token when subscribing since it was used during the handshake and this way avoid the second auth, but my thinking is that between the handshake and connection activation, there might be token update that we miss (it should be very rare but still possible) and end up with expired token. Also since we are targeting long running connections where we have number of reconnects, I think it is safer to leave the initial duplication of auth to avoid complex syncronisation.