Accept an arbitrary path to /migrations in config

[PSalant726]

Bug Description

PyPI installs the fidesops /migrations directory outside of the package source tree, in a sibling directory of /fidesops. Currently there is no way to specify a path to DB migrations that exists outside of the /fidesops package source tree.

Steps to Reproduce

1. pip install fidesops
2. docker run -it --rm fidesops_fidesops bash
3. Inside the container, observe:

   $ tree -L 2 /usr/local/lib/python3.9/site-packages/
   site-packages/
   ├─ fidesops/
   │  ├─ __init__.py
   │  ├─ ...
   ├─ migrations/
   │  ├─ versions/
   │  ├─ __init__.py
   │  ├─ ...
   ├─ ...
   

Expected behavior

Fidesops may accept an arbitrary file path to the /migrations directory via ENV variable configuration.

Additional context

This is required for fidesops-plus to start successfully.

[PSalant726]

Thinking more about the changes on #613, it might be better to simply move the /migrations directory inside of /fidesops instead. Thoughts @seanpreston @sanders41 ?

[sanders41]

I haven't seen migrations inside the package directory before, but this is a unique case. I think the idea of putting it in /fidesops makes sense here. pip install fidesops resulting in migrations being installed as it's own module in the virtual environment makes it unclear why the module is there, or where to find it when wanting to use it.

[PSalant726]

@sanders41

I haven't seen migrations inside the package directory before

It turns out that it's done this way in fidesctl. That's where I got the idea.

pip install fidesops resulting in migrations being installed as it's own module in the virtual environment makes it unclear why the module is there, or where to find it when wanting to use it.

I completely agree. Closing this issue and #613 in favor of #615.