lookup subdomain from the options hash once, defaulting to true
lookup subdomain from the options hash once, defaulting to true

if the subdomain wasn't specified, it's the same as if specifying
:subdomain as `true`, so we can default the value to `true` safely.

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otapatch/rails,lucasmazza/rails,prathamesh-sonpatki/rails,MichaelSp/rails,rails/rails,arunagw/rails,arjes/rails,shioyama/rails,samphilipd/rails,mtsmfm/railstest,BlakeWilliams/rails,mathieujobin/reduced-rails-for-travis,eileencodes/rails,illacceptanything/illacceptanything,mtsmfm/railstest,tjschuck/rails,georgeclaghorn/rails,illacceptanything/illacceptanything,tgxworld/rails,illacceptanything/illacceptanything,palkan/rails,coreyward/rails,betesh/rails,vipulnsward/rails,sergey-alekseev/rails,palkan/rails,yasslab/railsguides.jp,gavingmiller/rails,kachick/rails,georgeclaghorn/rails,bogdanvlviv/rails,notapatch/rails,MSP-Greg/rails,utilum/rails,rails/rails,printercu/rails,BlakeWilliams/rails,jeremy/rails,ttanimichi/rails,fabianoleittes/rails,Spin42/rails,amoody2108/TechForJustice,MSP-Greg/rails,travisofthenorth/rails,koic/rails,88rabbit/newRails,pschambacher/rails,starknx/rails,illacceptanything/illacceptanything,arunagw/rails,brchristian/rails,kddeisz/rails,maicher/rails,kmcphillips/rails,notapatch/rails,mohitnatoo/rails,schuetzm/rails,assain/rails,kirs/rails-1,coreyward/rails,odedniv/rails,yasslab/railsguides.jp,betesh/rails,alecspopa/rails,tgxworld/rails,lcreid/rails,vassilevsky/rails,MichaelSp/rails,maicher/rails