[Fixes #12167] providing multiple openid_connect django.allauth socialproviders fails when loading login page

[mwallschlaeger]

ref #12167, #12180

minor fix to allow mutiple APPS defined in an openid_connect , SOCIALACCOUNT_PROVIDERS. Further it includes check that client_id must be set.

closes #12167
closes #12180

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[codecov]

Codecov Report

Merging #12169 (6f5a2ca) into master (3d6ab6e) will not change coverage.
The diff coverage is 0.00%.

Additional details and impacted files

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  Coverage   64.04%   64.04%           
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  Files         870      870           
  Lines       52178    52178           
  Branches     6483     6483           
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  Hits        33418    33418           
  Misses      17259    17259           
  Partials     1501     1501           

[mwallschlaeger]

I go to continue work on this PR trying to fix also: #12180

[mwallschlaeger]

still in draft mode. There is still an issue connecting different openid_connect apps