docs: adjust documentation for registration approval process

[Phil91]

Description

Adjusting the registration approval process documentation

Why

The process has changed. New steps and a toggle for the sd factory call were introduced.

Issue

Refs: eclipse-tractusx/portal-backend#837

Checklist

• I have followed the contributing guidelines
• I have performed IP checks for added or updated 3rd party libraries
• I have created and linked IP issues or requested their creation by a committer
• I have added copyright and license headers, footers (for .md files) or files (for images)
• I have performed a self-review of my own code
• I have successfully tested my changes locally
• I have added tests that prove my changes work
• I have checked that new and existing tests pass locally with my changes
• I have commented my code, particularly in hard-to-understand areas