Buerklin provider

[mkne]

This pull request implements the Buerklin API and as Information Provider that also implements the BatchInfoProviderInterface.
Bürklin also offers an API. (Apply here: https://www.buerklin.com/de/services/eprocurement/)
Authorization works via Bearer Token that is requested via a POST-action to https://www.buerklin.com/authorizationserver/oauth/token/ and the following parameters:
client_id:cws-client
client_secret:{{PROVIDER_BUERKLIN_SECRET}}
grant_type:password
username:{{PROVIDER_BUERKLIN_USERNAME}}
password:{{PROVIDER_BUERKLIN_PASSWORD}}

There are only two GET-actions available:

Product search (example with the part number 66S447): https://www.buerklin.com/buerklinws/v2/buerklin/products/66S447/?curr=EUR&language=de
Free text search (example with the query string 'Resistor'): https://www.buerklin.com/buerklinws/v2/buerklin/products/search/?curr=EUR&language=en&pageSize=50&currentPage=0&query=Resistor&sort=relevance
I would set the parameters curr and language via PROVIDER_BUERKLIN_CURRENCY and PROVIDER_BUERKLIN_LANGUAGE.

Bürklin supplies a postman collection which I used to test the API and reverse engineer.
For reference: #868

[codecov]

Codecov Report

❌ Patch coverage is 66.99346% with 101 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.41%. Comparing base (98b8c5b) to head (c28c9b1).

Files with missing lines	Patch %	Lines
.../InfoProviderSystem/Providers/BuerklinProvider.php	66.99%	101 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1151      +/-   ##
============================================
+ Coverage     58.31%   58.41%   +0.10%     
- Complexity     7294     7384      +90     
============================================
  Files           580      581       +1     
  Lines         23207    23513     +306     
============================================
+ Hits          13534    13736     +202     
- Misses         9673     9777     +104     

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