[api] Add support of content_ref in Stix file for Artifact

[Kedae]

No description provided.

[codecov]

Codecov Report

Base: 71.78% // Head: 71.84% // Increases project coverage by +0.06% 🎉

Coverage data is based on head (b5c0bdb) compared to base (22326e0).
Patch coverage: 88.46% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2468      +/-   ##
==========================================
+ Coverage   71.78%   71.84%   +0.06%     
==========================================
  Files         238      238              
  Lines       15534    15540       +6     
  Branches     2516     2518       +2     
==========================================
+ Hits        11151    11165      +14     
+ Misses       3802     3795       -7     
+ Partials      581      580       -1     

Impacted Files	Coverage Δ
...-platform/opencti-graphql/src/generated/graphql.ts	100.00% <ø> (ø)
.../opencti-graphql/src/schema/stixCyberObservable.js	100.00% <ø> (ø)
...encti-graphql/src/resolvers/stixCyberObservable.js	51.51% <60.00%> (-0.05%)	⬇️
.../opencti-graphql/src/domain/stixCyberObservable.js	45.32% <88.23%> (+0.25%)	⬆️
...ncti-platform/opencti-graphql/src/database/stix.ts	89.90% <89.47%> (+4.19%)	⬆️
...latform/opencti-graphql/src/database/middleware.js	81.94% <100.00%> (+0.25%)	⬆️
...orm/opencti-graphql/src/database/stix-converter.ts	64.44% <100.00%> (ø)
...opencti-graphql/src/schema/stixCoreRelationship.ts	100.00% <100.00%> (ø)
...phql/src/schema/stixCyberObservableRelationship.ts	100.00% <100.00%> (ø)

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[richard-julien]

Early remarks

UI modification for content_ref is missing
stixCyberObservableEdit > addRelation (del ..._ are not working. (not related to this task but could be fixed)