SEO functionality backport for skosmos 2

[osma]

Reasons for creating this PR

Some new SEO / social media sharing features were implemented for Skosmos 3 in several PRs related to issue #1533. This PR is a backport of these features to Skosmos 2.

Link to relevant issue(s), if any

• related to Search Engine Optimization for Skosmos 3.0 #1533

Description of the changes in this PR

Contains commits cherry-picked and/or adapted from the following PRs that were made for Skosmos 3:

• SEO: improved titles for Skosmos 3 generated HTML pages #1625
• SEO: long title on landing page (skosmos:serviceNameLong configuration setting) #1644
• SEO: descriptions on landing, about and feedback pages #1647
• SEO: vocab description, site name, type, canonical URL #1657
• SEO: add description metadata to concept page #1659

The Twig template code changes had to be rewritten because Skosmos 2 has a very different template structure than Skosmos 3. While doing this, I decided to merge meta.twig into light.twig. I also created a separate landing.twig template; previously light.twig was used both as a base template and as the template for the landing page, but this wasn't flexible enough for implementing the meta descriptions.

Known problems or uncertainties in this PR

None so far 🤞

Checklist

• phpUnit tests pass locally with my changes
• I have added tests that show that the new code works, or tests are not relevant for this PR (e.g. only HTML/CSS changes)
• The PR doesn't reduce accessibility of the front-end code (e.g. tab focus, scaling to different resolutions, use of .sr-only class, color contrast)
• The PR doesn't introduce unintended code changes (e.g. empty lines or useless reindentation)

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
1.2% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.

Project coverage is 70.39%. Comparing base (7a53972) to head (e3c6de4).
Report is 23 commits behind head on skosmos-2.

Files	Patch %	Lines
controller/WebController.php	50.00%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##             skosmos-2    #1666      +/-   ##
===============================================
+ Coverage        70.33%   70.39%   +0.06%     
- Complexity        1669     1674       +5     
===============================================
  Files               32       32              
  Lines             4305     4314       +9     
===============================================
+ Hits              3028     3037       +9     
  Misses            1277     1277              

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[joelit]

The minor quip is that we have only the translation strings for "Concept X" in different languages, whereas it look a bit weird in cases where the data is instances or classification:

• Skosmos2/ykl/en/page/2
  • "Concept RELIGION in vocabulary PLC - Finnish Public Libraries Classification System"
  • Could be currently generated as "YKL Class RELIGION ..."
• Skosmos2/finaf/en/page/000179638
  • "Concept A. Aallon Rytmiorkesteri in vocabulary KANTO - Kansalliset toimijatiedot"
  • Could be currently merely generated as "Yhteisö A. Aallon Rytmiorkesteri ..." as there's no translation for the concept type in english in the data

One way would be to omit the word "Concept" but it's a minor thing.

[osma]

Good point! This was part of the speccing done earlier. I guess we didn't consider classifications back then.

[joelit]

Works as expected. I encountered some minor awkwardness in the wordings of the descriptions in concept page that I hadn't spotted before. Could be a subject for further improvement.