OpenAPI: Include jsonapi element or not, depending on options

[bkoelman]

fixes #1061.

QUALITY CHECKLIST

• Changes implemented in code
• Complies with our contributing guidelines
• Adapted tests
• N/A: Documentation updated

[codecov]

Codecov Report

Merging #1365 (2c1869f) into openapi (0709ea4) will increase coverage by 0.01%.
The diff coverage is 95.23%.

@@             Coverage Diff             @@
##           openapi    #1365      +/-   ##
===========================================
+ Coverage    90.05%   90.07%   +0.01%     
===========================================
  Files          306      306              
  Lines         9888     9904      +16     
  Branches      1660     1661       +1     
===========================================
+ Hits          8905     8921      +16     
  Misses         651      651              
  Partials       332      332              

Files	Coverage Δ
...enApi/JsonApiActionDescriptorCollectionProvider.cs	88.15% <100.00%> (+0.15%)	⬆️
...JsonApiMetadata/JsonApiEndpointMetadataProvider.cs	92.15% <100.00%> (+0.15%)	⬆️
...OpenApi/JsonApiMetadata/RelationshipTypeFactory.cs	100.00% <100.00%> (ø)
...enApi/SwaggerComponents/CachingSwaggerGenerator.cs	100.00% <ø> (ø)
...penApi/SwaggerComponents/JsonApiSchemaGenerator.cs	100.00% <100.00%> (ø)
...ggerComponents/NullableReferenceSchemaGenerator.cs	92.06% <ø> (ø)
...enApi/SwaggerComponents/OpenApiSchemaExtensions.cs	80.00% <100.00%> (+5.00%)	⬆️
...ggerComponents/ResourceFieldObjectSchemaBuilder.cs	99.03% <100.00%> (+0.01%)	⬆️
...SwaggerComponents/ResourceObjectSchemaGenerator.cs	93.75% <100.00%> (+0.09%)	⬆️
...nApi/SwaggerComponents/SchemaRepositoryAccessor.cs	66.66% <0.00%> (ø)