🐛 Fixed duplicate tags created when slugs contain spaces

[SimonBackx]

refs https://github.com/TryGhost/Team/issues/1284

• Matching tags by slug has been updated to work for slugs with spaces
• Also added a test to check slugs that are longer than 185 characters (since that will cause the same issue)
• Now, the tag slug gets filtered before doing any matching unless a tag id (or foreign key) is set when creating or editing posts.
• Added skipDuplicateChecks option to generateSlug model plugin.
• Added tests

Edge case

Say that we have an existing tag: {slug: 'my-slug', name: 'This is my slug'}

When you create a new post like this:
api.posts.add({title: 'test post', tags: [{slug: 'my slug'}]})

The current solution is to transform it into the following query in the onSaving event of Post:
api.posts.add({title: 'test post', tags: [{slug: 'my-slug'}]})

This works! But the only downside is, that when creating a new tag, it creates it with the name 'my-slug' instead of 'my slug'.

To work around this issue there needs to be a way for bookshelf-relations to have a different matching logic (to search for existing tags), separate from the insert logic (when creating new tags). Currently you cannot match existing tags on the slug my-slug (and not match on name my slug at the same time), while setting the name to my slug when inserting (but not when updating an existing tag). This gets far too complex for this small issue, since the user can just change the name afterwards.

[codecov]

Codecov Report

Merging #14277 (b355b9d) into main (d8295da) will decrease coverage by 0.00%.
The diff coverage is 46.42%.

@@            Coverage Diff             @@
##             main   #14277      +/-   ##
==========================================
- Coverage   55.48%   55.48%   -0.01%     
==========================================
  Files         565      565              
  Lines       46840    46862      +22     
  Branches     3899     3898       -1     
==========================================
+ Hits        25991    26003      +12     
- Misses      20810    20820      +10     
  Partials       39       39              

Impacted Files	Coverage Δ
core/server/models/post.js	36.31% <6.66%> (-0.21%)	⬇️
core/server/models/base/plugins/generate-slug.js	85.95% <92.30%> (+0.62%)	⬆️

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