Harden Redis store semantics and align CI/tooling

[rmarronnier]

This shard needed a big refresh.

About luckyframework/lucky_cache#17 :

This shard already supports those same array/basic types:

• scalar support in src/lucky_cache_redis_store/redis_store.cr:86
• array serialization/deserialization in src/lucky_cache_redis_store/redis_store.cr:173, src/
  lucky_cache_redis_store/redis_store.cr:222, and src/lucky_cache_redis_store/redis_store.cr:271
• regression coverage in spec/lucky_cache_redis_store/redis_store_spec.cr:65 and spec/
  lucky_cache_redis_store/redis_store_spec.cr:137

The important caveat is that it is not identical to MemoryStore overall:

• RedisStore still does not support arbitrary custom LuckyCache::Cachable objects.
• RedisStore also does not support arbitrary Array(Cachable) collections.

[jwoertink]

Nice!

For that failure on 1.16, Timecop has to be locked to v0.5.0 I think. They made a change that requires Crystal 1.19 or later. If you can just add the version: ~> 0.5.0 to that, then I think it'll be good

[jwoertink]

Sweet!