Add day resolver to Conference to filter slots by date

[estyxx]

#1578

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Codecov Report

Merging #1586 into master will increase coverage by 0.00%. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1586   +/-   ##
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  Coverage   99.91%   99.91%           
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  Files         114      114           
  Lines        2356     2359    +3     
  Branches      214      214           
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+ Hits         2354     2357    +3     
  Partials        2        2