feat: support --fake for aerich upgrade (#398)

* feat: support `--fake` for aerich upgrade

* Add `--fake` to downgrade

* tests: check --fake result for aerich upgrade and downgrade

* Update readme

* Fix unittest failed because of `db_field_types` changed

* refactor: improve type hints and document

tests/assets/fake/db.py

@@ -0,0 +1,28 @@
+import asyncclick as click
+from settings import TORTOISE_ORM
+
+from tests._utils import drop_db, init_db
+
+
+@click.group()
+def cli(): ...
+
+
+@cli.command()
+async def create():
+    await init_db(TORTOISE_ORM, False)
+    click.echo(f"Success to create databases for {TORTOISE_ORM['connections']}")
+
+
+@cli.command()
+async def drop():
+    await drop_db(TORTOISE_ORM)
+    click.echo(f"Dropped databases for {TORTOISE_ORM['connections']}")
+
+
+def main():
+    cli()
+
+
+if __name__ == "__main__":
+    main()