Nullable meta annotations are ignored

[Sam-Kruglov]

Describe the feature
JSR 303 allows for creating a constraint composition and it seems to not be supported. I can see the code responsible in org.springdoc.core.AbstractRequestService#applyBeanValidatorAnnotations and in io.swagger.v3.core.jackson.ModelResolver#applyBeanValidatorAnnotations.

To Reproduce
Steps to reproduce the behavior:

• What version of spring-boot you are using?
  2.4.0
• What modules and versions of springdoc-openapi are you using?
  openapi-ui, and security
• What is the actual and the expected result using OpenAPI Description (yml or json)?
  A schema that contains @NotBlank inside a meta-annotation is not marked as required but should be.
• Provide with a sample code (HelloController) or Test that reproduces the problem.

@Max(255)
@NotBlank
@Documented
@Constraint(validatedBy = {})
@Target({METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER, TYPE_USE})
@Retention(RUNTIME)
@interface UserFirstOrSecondName {

    String message() default "Invalid name";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};
}

@lombok.Value
class UserDto{
  @UserFirstOrSecondName String firstName;
}

@RestController
@RequestMapping("/users")
class UserControlle{
  @PostMapping
  void createUser(@Valid @RequestBody UserDto user){...}
}

Expected behavior

CreateUserDto:
      properties:
        firstName:
          type: string
      required:
        - firstName # this is missing
      type: object

Additional context
Also, I see that ModelResolver compares annotations by their simple name, while AbstractRequestService contains raw classes and there is only JSR 303 support (i.e. some annotations won't be picked like JSR 305, spring, jetbrains, findbugs, etc). I think that it'd be better to use simple names here as well. But I am not sure if this bug is actually in the swagger project

[bnasslahsen]

This is not a bug but a feature request.

Only JSR 303 annotations are supported in the documentation.

• springdoc-openapi scans for these annotations in the parameter level.
• The scan for the class attributes annotations is done directly by the swagger-core library as you have read on on the ModelResolver class.
  It makes more sense to add the support of meta-annotations of JSR 303 annotation on the class attributes in the swagger-core library instead.

The usage of strict JSR 303 annotations simple name, have the advantage of controlling the naming of annotations that are used and not introducing any Undesirable annotations to be treated as a standard one.

Ok, for opening the scan for other annotations, if they use the same naming (even this might cause undesirable controls which might be applied if the annotation naming is the same of none standard one).

If necessary, we can add an option to disable this control or simply revert this change back.