Fix: The sub length of the dex user more than 31

[barnettZQG]

Description of your changes

Fixes #784

I have:

• Read and followed KubeVela's contribution process.
• Related Docs updated properly. In a new feature or configuration option, an update to the documentation is necessary.
• Run yarn lint to ensure the frontend changes are ready for review.
• Run make reviewableto ensure the server changes are ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

Special notes for your reviewer

[codecov]

Codecov Report

Patch coverage: 62.50% and project coverage change: +0.04 🎉

Comparison is base (b0c407f) 61.07% compared to head (00e3717) 61.11%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #785      +/-   ##
==========================================
+ Coverage   61.07%   61.11%   +0.04%     
==========================================
  Files         109      109              
  Lines       19141    19142       +1     
==========================================
+ Hits        11690    11699       +9     
+ Misses       5998     5995       -3     
+ Partials     1453     1448       -5     

Flag	Coverage Δ
apiserver-unittests	33.79% <62.50%> (+0.09%)	⬆️
server-e2e-tests	49.71% <12.50%> (-0.07%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/server/infrastructure/datastore/datastore.go	78.57% <ø> (ø)
pkg/server/domain/service/authentication.go	50.37% <57.14%> (+0.62%)	⬆️
pkg/server/interfaces/api/validate.go	51.56% <100.00%> (ø)

... and 8 files with indirect coverage changes

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[github-actions]

Successfully created backport PR #788 for release-1.8.