ResponseValidation cannot handle case insensitive headers

[pk-work]

OpenAPI spec snippet

      responses:
        '201':
          description: Entity created successfully
          headers:
            Location:
              description: URL of the newly created resource
              schema:
                type: string

ValidatableResponse resp = ValidatableResponse.create(201, Map.of("location", "https://example.org/entities/1337"))
// ...
// ...
responseValidator.validate(validatableResponse, operationId)) // fails because header "Location" wasn't found.
.compose(validatedResponse -> validatedResponse.send(routingContext.response())) // send method will not add "location" header to the response, because header  "Location" wasn't found.