Support djangocms-picture 2.0.0 and higher in create_picture_plugin

[leture]

djangocms-picture 2.0.0 switched to a filer reference to store the image so the helper must create a filer image instance

Refs #642

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2e463bf) 76.36% compared to head (5b02c31) 81.79%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #660      +/-   ##
==========================================
+ Coverage   76.36%   81.79%   +5.43%     
==========================================
  Files          20       20              
  Lines         918      912       -6     
  Branches      123      122       -1     
==========================================
+ Hits          701      746      +45     
+ Misses        191      138      -53     
- Partials       26       28       +2     

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[fsbraun]

@leture Do you think you can cover this in a test?

[leture]

@fsbraun Because of the lack of an existing test to just adjust I wrote a test for the helper extract_images which subsequently also tests create_picture_plugin. This seemed to be more worthwhile than just a direct call to create_picture_plugin. So it is tested that the image extraction logic is actually executed on a text plugin save.

[leture]

@fsbraun I am finished here.

[fsbraun]

Very nice! Looks good to me. I have just a minor recommendation. Thank you so much, @leture!