fix (app): prevent excess sync() calls during db seed

Previously, .sync() was being called once in server/config/seed.js and once during sqldb.sequelize.sync() in server/app.js. As a result, duplicate queries were being sent to the database if the tables needed to be defined causing an error when it tries to define constraints a second time (like for an identity column).

Seed.js is wrapped in a function and contains the conditional to determine whether to seed the database. This makes it easy to include in the promise chain under sqldb.sequelize.sync().

Author: nstuyvesant

Diff for: templates/app/server/app.js

@@ -44,6 +44,7 @@ sqldb.sequelize.sync()
     console.log('Server failed to start due to error: %s', err);
   });
 <% } else { %>
+seedDatabaseIfNeeded();
 setImmediate(startServer);
 <% } %>
 // Expose app