fix lectures creating errors

[rodlukas]

https://www.django-rest-framework.org/community/release-notes/#3150 - prechod z OrderedDict na dict zpusobil nefunkcni pridavani lekci

[sentry-io]

🔍 Existing Issues For Review

Your pull request is modifying functions with the following pre-existing issues:

📄 File: api/serializers.py

Function	Unhandled Issue
create	AttributeError: 'dict' object has no attribute 'paid' /api/v1/lect... Event Count: 5

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 84.77%. Comparing base (17849e1) to head (c320f4b).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
api/serializers.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #188   +/-   ##
=======================================
  Coverage   84.77%   84.77%           
=======================================
  Files          11       11           
  Lines         624      624           
=======================================
  Hits          529      529           
  Misses         95       95           

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