Use 302 instead of 301 when redirecting for an invalid lang

[diox]

Fixes mozilla/addons#15758

We are enabling/disabling locales depending on whether their completion percentage so a permanent (301) redirect could be problematic.

The caching duration could still be an issue, but at least the non-permanent nature of the redirect should make things easier, and it's more consistent with addons-server which was already using a 302 (with that same caching duration).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.15%. Comparing base (3854bdb) to head (caacbd8).
⚠️ Report is 5 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #13929   +/-   ##
=======================================
  Coverage   98.15%   98.15%           
=======================================
  Files         265      265           
  Lines       10661    10664    +3     
  Branches     3274     3275    +1     
=======================================
+ Hits        10464    10467    +3     
  Misses        184      184           
  Partials       13       13           

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[eviljeff]

It's kind of weird when you go to http://127.0.0.1:3333/en-GC/ you get redirected to http://127.0.0.1:3333/en-GB/firefox/en-GC/ rather than http://127.0.0.1:3333/en-GB/firefox/ but that's existing behaviour.

That redirect is still a 301 though - should it also be a 302?

[diox]

Yeah I wasn't sure if we wanted to also change that one... I guess we do.