fix: enum type of session expandables

[jonas-jonas]

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• 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 the approval (please contact
  security@ory.sh) 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 or changed the documentation.

Further Comments

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.05%. Comparing base (9c69ef2) to head (9f44e77).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3891      +/-   ##
==========================================
+ Coverage   78.03%   78.05%   +0.01%     
==========================================
  Files         360      360              
  Lines       25246    25246              
==========================================
+ Hits        19701    19705       +4     
+ Misses       4037     4032       -5     
- Partials     1508     1509       +1     

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