fix: RedisStore with no expiration

[speedytwenty]

I was unable to get the RedisStore to work no-expiration. Setting the maxAge to 0 seemed to lead to immediate expiration and setting the maxAge to Number.POSITIVE_INFINITY resulted in expires value being null.

So to solve this, I'm passing Number.POSITIVE_INFINITY as the maxAge and the RedisStore adjusts the expires value to 0.

This fix does feel a bit hackish. I can make adjustments if someone can point out a cleaner way to solve this.

[codecov]

Codecov Report

Merging #259 (9afc56c) into master (2d51cee) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #259   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           13        13           
  Lines          235       235           
=========================================
  Hits           235       235           

Impacted Files	Coverage Δ
src/redis.js	100.00% <100.00%> (ø)
src/serialize.js	100.00% <0.00%> (ø)

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