title: EF Migrations in orchestrator (eShopOnContainers)
body: <p>Looking at eShopOnContainers, the microservice reference architecture from Microsoft.  I see that for each service, in Program.cs a call is made to host.MigrateDbContext.  This, in turn, executes all of the EF migrations for the given context.</p>
  
  <p>In a real-world orchestrator isn't is possible that numerous containers for the same service could be spun up almost simultaneously?  And if that happened, isn't it likely that multiple containers trying to execute the same migrations would deadlock or cause other issues?</p>
  
  <p>Is this something that wasn't dealt with because it is beyond the scope of a reference project or does EF have something built in to handle concurrency that I'm not seeing?</p>