Add __dir__ to configuration file

[tobiasge]

Related Issue: #653

New Behavior

• All configuration values from all imported files are listed and can be used from Netbox

Contrast to Current Behavior

• New SOCIAL_AUTH_* parameters are ignored

Discussion: Benefits and Drawbacks

It is now possible to set all configuration values from extra files.

Changes to the Wiki

• None

Proposed Release Note Entry

• New SOCIAL_AUTH_* parameters can be configured from extra config files

Double Check

• I have read the comments and followed the PR template.
• I have explained my PR according to the information in the comments.
• My PR targets the develop branch.

[cimnine]

No idea how it works, but it's been a while since I wrote that configuration magic. I've also seen the comment in the issue and trust you, that it does (just) the right thing 👍

[tobiasge]

Alpine edge checks can be ignored as we are switching to Debian soon (I hope).