fix: do not process a nullable annotation for container items

[Mattias-Sehlstedt]

Pull Request

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Description

Fixes part of the issue reported in #5077 where the items within a List (container) are affected by a @Nullable annotation. I.e.,

@Nullable
List<String> listOfStrings

This should only mark the list itself as nullable, while the items would be controller either by an explicit @ArraySchema annotation or something similar to

List<@Nullable String> listOfStrings

*Although @Nullable does not apply to a Type field)

This change is achieved by making sure that @Nullable is dropped when annotations are forwarded for a container type field.

The second part of issue #5077 is not handled, where #ref:s are not correctly marked as nullable.

I have intentionally not handled that in this PR since that is a much larger task, since the issue is that there does not seem to exist any framework to support expressing that. I.e., either having

schema:
  allOf:
    - $ref: '#/components/schemas/User'
  nullable: true

for OAS 3.0 or

schema:
  oneOf:
    - $ref: '#/components/schemas/User'
    - type: 'null'

or

schema:
  type: [object, "null"]
  $ref: '#/components/schemas/User'

for OAS 3.1.

Fixes:

Type of Change

• 🐛 Bug fix
• ✨ New feature
• ♻️ Refactor (non-breaking change)
• 🧪 Tests
• 📝 Documentation
• 🧹 Chore (build or tooling)

Checklist

• I have added/updated tests as needed
• I have added/updated documentation where applicable
• The PR title is descriptive
• The code builds and passes tests locally
• I have linked related issues (if any)

Screenshots / Additional Context