feat: add SCIM docs

[hperl]

Related Issue or Design Document

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact [email protected]) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

Further comments

[vinckr]

nice!
a few comments, did not test anything ofc

[vinckr]

looks good to me looking at the text,
did not test the feature.
will it have separate API docs as well in our reference docs?

[christiannwamba]

Looks good to me. Just a nitpicked typo.

all fixed :)