🐛(rdfa) fix errors on Google Search Console

[igobranco]

Google Search Console requires more information for the RDFa information.

Fixes 2 of 3 problems identified by #2444:

• [X] Missing field 'hasCourseInstance'
• [X] Either 'courseWorkload' or 'courseSchedule' should be specified (in 'hasCourseInstance')

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To validate copy paste a course page html code to the Google Search Console validator: https://search.google.com/test/rich-results/result

[igobranco]

@jbpenrath I've updated this PR description, because this PR only fixes 2 of 3 problems identified by #2444. Can you review again so we can merge it?

[igobranco]

@jbpenrath I have remember that course runs can be hidden with the catalog_visibility field. I have added an if to skip those runs on the RDFa. Additionally, I have found out that the course enrollment_count total, wasn't skipping the hidden runs...

I've also included a new test for the courseWorkload RDFa.

[igobranco]

@jbpenrath do you want me to split the commit into 2 different fixes?

[jbpenrath]

@jbpenrath do you want me to split the commit into 2 different fixes?

Yes good idea!

[igobranco]

@jbpenrath do you want me to split the commit into 2 different fixes?

Yes good idea!

@jbpenrath I've splitted the commits! I think everything is done! Please done a last review so we can merge it! Thanks you with your effort on this!