Wrong schema generation with PagedModel generated VIA_DTO and wrapped in ResponseEntity

[Gianpiero-3di]

The bug involves this PR
#2626

It works when the page is directly returned by the controller, but if wrapped in a ResponseEntity the generated schema for PagedModel's content is generic object instead of the DTO passed as type.

I tracked down the issue to
dd30b9d#diff-aa17a2514af0e0de9a296e748f33bffb9baa551038dcfbf2f959a46bc20764b1R96
where the the block responsible for typing page content is put behind a instanceof check that will fail for ResponseEntity wrapped response, because the pageType gets recognized as SimpleType unlike what happens when the Page is returned directly, where pageType results of ParameterizedType.

Steps to reproduce the behavior:

• SpringBoot 3.4
• springdoc-openapi-starter-webmvc-ui 2.8.5

public record UserDto(
    String id,
    String email,
)

@RestController
public class HelloController {	
  @GetMapping("/page-simple")
	public ResponseEntity<Page<UserDto>> pageSimple() {
		return ResponseEntity.ok(pageImpl(new UserDto("someId", "someName")));
	}
}

	@SpringBootApplication
	@EnableSpringDataWebSupport(pageSerializationMode = EnableSpringDataWebSupport.PageSerializationMode.VIA_DTO)
	public static class SpringDocTestApp {

	}

Expected behavior

current schema

...
"responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/PagedModel"
                }
              }
            }
          },
...
      "PagedModel": {
        "type": "object",
        "properties": {
          "content": {
            "type": "array",
            "items": {
              "type": "object"
            }
...

expected schema

...
"responses": {
          "200": {
            "description": "OK",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/PagedModelUserDto"
                }
              }
            }
          },
...
"PagedModelUserDto": {
        "type": "object",
        "properties": {
          "content": {
            "type": "array",
            "items": {
              "$ref": "#/components/schemas/UserDto"
            }
...

Issue is not present returning a ResponseEntity<PagedModel> explicitly

return ResponseEntity.ok(new PagedModel(pageImpl(new UserDto("someId", "someName"))));

but that completely defeats the goal of the VIA_DTO configuration