Return 404 for releases missing author, e.g. /release//File-Stat-Convert instead of a 500

[haarg]

Fixes #3155

[haarg]

This is an alternative to #3156. Instead of checking and rejecting an empty author, this adds type constraints to the routing. A path that we don't want to handle will just fall out as unroutable and thus give a 404. This style should nicer to use in more places, rather than having to put explicit checks and 404 redirects all over the code.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.07%. Comparing base (9059e9d) to head (e61bdd9).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3157      +/-   ##
==========================================
+ Coverage   72.85%   73.07%   +0.22%     
==========================================
  Files          69       69              
  Lines        2391     2392       +1     
  Branches      338      338              
==========================================
+ Hits         1742     1748       +6     
+ Misses        521      518       -3     
+ Partials      128      126       -2     

Files	Coverage Δ
lib/MetaCPAN/Web/Controller/Release.pm	90.19% <100.00%> (+0.09%)	⬆️

... and 3 files with indirect coverage changes

[ranguard]

Nice, it is what I wanted to do but didn’t know how!