THREESCALE-8404: Add ACL and TLS support for Redis

[jlledom]

This supersedes https://github.com/3scale/apisonator/pull/350. That PR is too messy and contains a lot of wrong or outdated info.

Jira Issue:

THREESCALE-8404

Summary of changes:

• Implement support for ACL and TLS (https://github.com/3scale/apisonator/commit/914f97c59faf0be8cbdef5cf9323bccd640aaded):
  • The existing async client (StorageAsync::Client) is very simple now. It got too complex due to all scenarios it must support, so I extracted most of its logic to the new class AsyncRedis::Client.
  • AsyncRedis::Client is a wrapper for the two Redis clients we use in async mode: one for single instances and one for sentinels. This implements support for all possible scenarios.
  • AsyncRedis::EndpointHelpers is a utility module which contains some logic that is used from several places.
  • Our custom protocol AsyncRedis::Protocol::ExtendedRESP2 now accepts ACL credentials.
  • We also use our own client for Sentinels: AsyncRedis::SentinelsClientACLTLS which extends the upstream client Async::Redis::SentinelsClient to add it ACL and TLS support.
• Add new ENV variables to configure ACL and TLS (https://github.com/3scale/apisonator/commit/8104713eb612f1d3f4d95f83f62d8a10fb80cb22):
  • These new variables are going to be set directly from the operator.
  • Check: THREESCALE-11020 and THREESCALE-11021.
• Update tests (https://github.com/3scale/apisonator/commit/a7ddc79e76a84ca5ea762704f1edf874d25b25d8):
  • It installs fakefs. This is used to dynamically generate RSA, DSA and EC keys to be tested from StorageAsyncTest. In async mode we only support these 3 algorithms for TLS but I think that's enough for most of cases and we can add new algorithms in the future if some client requires it.
  • TestHelpers::Certificates contains the logic to generate keys and certificates for tests.
  • Added TLS and ACL tests in StorageAsyncTest and StorageSyncTest.

[jlledom]

@akostadinov I made some changes from your comments.

[jlledom]

@akostadinov I think I addressed all your comments.