Fix creating parts from TME if the SPN contains percent signs

[alufers]

Example: https://www.tme.eu/en/details/smd0603-5k1-1%25/smd-resistors/royalohm/0603saf5101t5e/

The TME API returns an URL for that part which contains an unencoded percent sign, this later causes a form validation error when trying to save the added part.

Fixed by percent encoding it if detected. Also added unit tests for the TMEProvider.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.91%. Comparing base (96da2b9) to head (a088fbc).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1337      +/-   ##
============================================
+ Coverage     56.39%   56.91%   +0.52%     
  Complexity     8345     8345              
============================================
  Files           612      612              
  Lines         26801    26802       +1     
============================================
+ Hits          15115    15255     +140     
+ Misses        11686    11547     -139     

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