Create custom command to validate existing plugins on server

[sumandari]

Please see #178

This PR to validate the existing plugins on server, which has been uploaded before the metadata validation function fixed.
Custom command will send email to the creator and author of invalid plugins.

[codecov-commenter]

Codecov Report

Merging #179 (23fea87) into master (222b10d) will increase coverage by 5.44%.
The diff coverage is 88.44%.

@@            Coverage Diff             @@
##           master     #179      +/-   ##
==========================================
+ Coverage   68.21%   73.66%   +5.44%     
==========================================
  Files         102      108       +6     
  Lines        3886     4162     +276     
==========================================
+ Hits         2651     3066     +415     
+ Misses       1235     1096     -139     

Impacted Files	Coverage Δ
...s/management/commands/validate_existing_plugins.py	66.66% <66.66%> (ø)
qgis-app/plugins/views.py	30.07% <77.77%> (+11.46%)	⬆️
qgis-app/plugins/tests/test_views.py	89.55% <89.55%> (ø)
qgis-app/plugins/migrations/0002_plugininvalid.py	100.00% <100.00%> (ø)
qgis-app/plugins/models.py	81.31% <100.00%> (+20.12%)	⬆️
qgis-app/plugins/tests/model_factories.py	100.00% <100.00%> (ø)
qgis-app/plugins/tests/test_models.py	100.00% <100.00%> (ø)
...pp/plugins/tests/test_validate_existing_plugins.py	100.00% <100.00%> (ø)
qgis-app/plugins/urls.py	100.00% <100.00%> (ø)
... and 10 more

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[timlinux]

@sumandari I didnt look at the code, but it probably makes sense to only look at the latest version of each plugin - can you confirm if it does that?

[timlinux]

Also it would be nice to have view or something of plugins whose latest version fails validation so that we can keep track of which ones are still problematic as fixes come in....

[sumandari]

[sumandari]

Once we run management command, it will create invalid plugin list.
When the plugin version updated and add new plugin version(with validation mechanism upon upload), it will be removed from invalid plugin list.

[timlinux]

LGTM thanks @sumandari !

[dimasciput]

@Xpirix could you check if this is still useful?

[Xpirix]

@dimasciput , we didn't receive any issues similar to #177 recently. This PR will list all the plugins that are uploaded before the metadata validation and didn't have new versions since. I can check locally to see how many plugins are invalid.

[Xpirix]

@dimasciput @timlinux

After checking locally, I think it's still useful to have the list of invalid plugins because the validation workflow has changed over time so we will also be able to see others that don't meet the current requirements (plugins that don't have a license file for example).

However, I have a few questions:

• Some of the plugins are no longer maintained (the latest versions were uploaded 10 years ago and support for QGIS < 2.0) and are not marked as deprecated yet (https://plugins.qgis.org/plugins/FastSQL/ for example). Looking at the Github repo, it seems that the author doesn't have the time resources to maintain it anymore. So I wanted to ask if we could add to the email a section that (1) encourages the author to upload a new version that matches the current requirements, (2) notifies the author that the plugin will automatically be marked as deprecated if no new version is uploaded after X months,
• Could apply the above suggestion for invalid plugins that don't have new versions after X years old, and/or don't have support for QGIS > X.XX ?
• Could we implement this feature after the migration to the new branding? So we don't have to do it twice (here and on the new repo).