Prep to remove Readthis in favor of ActiveSupport::Cache::RedisCacheStore

[zachmargolis]

• Also just use plain redis connections elsewhere in the app

Builds on #5335 (because that renamed REDIS_POOL to READTHIS_POOL) --- happy to flip the order on these if anybody feels strongly

[zachmargolis]

🚨 ok so this is going to be a doozy ---- the Readthis gem serializes and deserializes via Marshal (😭) and also does some compression, and we use this for important data that is not strictly caching (ServiceProviderRequests and proofing intermediate results), so we need to handle this carefully

I think we have a few options:

1. Leave in this gem forever because data migration is scary
2. Write our own code that reads/writes the Marshal + Deflate compression to migrate
3. Dual reads/write: leave in gem while we read from old locations, but then always write to newer locations (ex with JSON serialization)

I think 3 is the safest and helps us minimize our dependencies

[zachmargolis]

I'm going with (3), but also going to namespace the new writes to make sure we don't write to JSON parse Marshal'd data or otherwise

[mitchellhenke]

3 makes sense and is the lowest risk 👍🏼

[zachmargolis]

the namespace should separate new data from old data, it means there will essentially be a reset on the rack-attack values after a deploy, but I think the timeouts are short-lived enough things will be okay?

[zachmargolis]

This is ready to review!