Display nullable request body with map type

[granddaifuku]

Fixes #2703

Problem Overview

@RestController
public class GreetController {
    @PostMapping("/greet")
    @Operation(summary = "Greet")
    public String greet(
            @io.swagger.v3.oas.annotations.parameters.RequestBody(description = "Some description", required = false)
            @RequestBody(required = false) Map<String, String> body) {
        return body.getOrDefault("greet", "Hello");
    }
}

In the example above, the request body is not displayed because it is marked as a parameter to ignore.
This behavior stems from the fact that the request body is both optional and of type java.util.Map.
The relevant code can be found here:

springdoc-openapi/springdoc-openapi-starter-common/src/main/java/org/springdoc/core/service/AbstractRequestService.java

Lines 451 to 457 in 03349cf

	public boolean isParamToIgnore(MethodParameter parameter) {
	if (SpringDocAnnotationsUtils.isAnnotationToIgnore(parameter))
	return true;
	if (isRequiredAnnotation(parameter))
	return false;
	return isRequestTypeToIgnore(parameter.getParameterType());
	}

springdoc-openapi/springdoc-openapi-starter-common/src/main/java/org/springdoc/core/service/AbstractRequestService.java

Line 141 in 03349cf

PARAM_TYPES_TO_IGNORE.add(java.util.Map.class);

Although this logic makes sense in some cases, I believe that using a Map as a request body is fairly common and should be supported, even when the request body is not required. As such, I’ve made an adjustment that ensures the request body will still be displayed when its type is Map.

I would love to hear your thoughts or feedback on this approach and whether you think it aligns with the project’s goals.