title: TypeORM - generate migrations from existings entites
body: <p>Got a nest.js/typeorm/postgres application that I have been developing for the last year. Been creating/adding/removing tables/columns but never used migrations.</p>
  <p>Now comes time to deploy and whenever I run <code>typeorm migration:generate</code>, a migration file is created for the last colums that I added/removed from only 1 or 2 tables.</p>
  <p>Is it possible to generate a migration for all existing entities that are already part of my db schema?</p>
  <p>Basically, the <code>up</code> would create each table with FKs, indexes, constraints, etc and the <code>down</code> would drop all of that.</p>
  <p>Note: I noticed <a href="https://github.com/typeorm/typeorm/issues/3188" rel="nofollow noreferrer">this</a> post. Is this the correct approach for my issue?</p>