[Transfer] Add connectors

[jflim]

Fixes #9816

[codecov]

Codecov Report

❌ Patch coverage is 95.50562% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.12%. Comparing base (b01bd65) to head (725a30f).

Files with missing lines	Patch %	Lines
moto/transfer/models.py	88.57%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #9835   +/-   ##
=======================================
  Coverage   93.12%   93.12%           
=======================================
  Files        1308     1308           
  Lines      118900   118987   +87     
=======================================
+ Hits       110722   110805   +83     
- Misses       8178     8182    +4     

Flag	Coverage Δ
servertests	28.87% <0.00%> (-0.03%)	⬇️
unittests	93.10% <95.50%> (+<0.01%)	⬆️

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