chore: use module api to set displayname

[itsoyou]

SYN-100

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 72.05%. Comparing base (4380174) to head (947c927).

Files with missing lines	Patch %	Lines
synapse_token_authenticator/token_authenticator.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #92   +/-   ##
=======================================
  Coverage   72.05%   72.05%           
=======================================
  Files           5        5           
  Lines         773      773           
  Branches      144      144           
=======================================
  Hits          557      557           
  Misses        157      157           
  Partials       59       59           

Files with missing lines	Coverage Δ
synapse_token_authenticator/token_authenticator.py	71.53% <66.66%> (ø)

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