[BUG] [JAVA] [SPRING] Optional values aren't optional in POJOs, only in path params

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

Optional values aren't optional in POJOs, only in path params.

openapi-generator version

5.3.0

OpenAPI declaration file content or url

modules/openapi-generator/src/test/resources/3_0/petstore-with-nullable-required.yaml

Generation Details

generatorName: spring
outputDir: samples/openapi3/server/petstore/springboot-nullable
inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore-with-nullable-required.yaml
templateDir: modules/openapi-generator/src/main/resources/JavaSpring
additionalProperties:
  groupId: org.openapitools.openapi3
  documentationProvider: springdoc
  artifactId: springboot
  snapshotVersion: "true"
  hideGenerationTimestamp: "true"
  openApiNullable: "true"
  useOptional: "true"

Steps to reproduce

Generate POJOs

Related issues/PRs

Suggest a fix

Update pojo.mustache to enable optional fields and any updates required for nullables

Start with modules/openapi-generator/src/main/resources/JavaSpring/pojo.mustache and reproduce generation using modules/openapi-generator/src/test/resources/3_0/petstore-with-nullable-required.yaml with useOptional and openApiNullable enabled. Compare generated POJOs with the path-parameter behavior and verify that optional and nullable fields are represented as intended.