Fixes #19589 - Added plugin migration generator
Now plugin creators would be able to generate migrations by invoking
``` sh
rails g plugin:migration <migration name and options> --plugin_name=my_plugin
```
Fixes #19589 - Added plugin migration generator
Now plugin creators would be able to generate migrations by invoking
``` sh
rails g plugin:migration <migration name and options> --plugin_name=my_plugin
```