[BUG][jaxrs-spec] Encoding issue

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?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When generating classes from openapi.yaml custom specification with french special characters, Swagger @ApiOperation "value" fields contain badly encoded special characters.
This is a problem for me because my API documentation inside Swagger-UI is well exposed but unreadable...
Indeed, "Récupérer la liste des titi" becomes "Récupérer la liste des titi".

openapi-generator version

I am usign 5.1.0 version of openapi-generator-maven-plugin

OpenAPI declaration file content or url

openapi.yaml

# OpenAPI 3.0.3 specification documentation: https://spec.openapis.org/oas/v3.0.3
openapi: 3.0.3

info:
  description: "API du toto"
  version: "1.0"
  title: Toto OpenAPI specification

paths:
  /toto/titi:
    get:
      summary: Récupérer la liste des titi
      operationId: findToto
      parameters:
      - name: page
        in: query
        description: Numéro de la page à afficher
        schema:
          type: integer
          minimum: 0
          default: 0
      - name: size
        in: query
        description: Nombre d'éléments à afficher par page
        schema:
          type: integer
          minimum: 1
          maximum: 10
          default: 10
      - name: sort
        in: query
        description: Champs avec lequel trié le resultat
        schema:
          type: string
          enum: [id, pacage, attribute, statut]
          default: id
      - name: order
        in: query
        description: Ordre de trie du resultat
        schema:
          type: string
          enum: [asc, desc]
          default: asc
      responses:
        200:
          description: La liste des titi
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "definitions.yaml#/definitions/Toto"

    post:
      summary: Insérer un nouveau toto
      operationId: insertToto
      requestBody:
        description: toto à insérer
        required: true
        content:
          application/json:
            schema:
              $ref: 'definitions.yaml#/definitions/Toto'
      responses:
        201:
          description: Le toto a été inséré

  /toto/titi/{idToto}:
    get:
      summary: Obtenir les détails du toto
      operationId: getToto
      parameters:
      - name: idToto
        in: path
        description: Identifiant du toto
        required: true
        schema:
          type: integer
          format: int64
      responses:
        200:
          description: Le toto demandé
          content:
            application/json:
              schema:
                $ref: "definitions.yaml#/definitions/Toto"

    put:
      summary: Mettre à jour un toto existant ou en insérer un nouveau
      operationId: updateToto
      parameters:
      - name: idToto
        in: path
        description: Identifiant du toto
        required: true
        schema:
          format: int64
          type: integer
      requestBody:
        description: toto à mettre à jour ou à insérer
        required: true
        content:
          application/json:
            schema:
              $ref: "definitions.yaml#/definitions/Toto"
      responses:
        200:
          description: toto a été mis à jour
        201:
          description: Le toto a été inséré

    delete:
      summary: Supprimer un toto existant
      operationId: deleteToto
      parameters:
      - name: idToto
        in: path
        description: Identifiant du toto
        required: true
        schema:
          format: int64
          type: integer
      responses:
        200:
          description: toto a été supprimé

definitions.yaml

# OpenAPI 3.0.3 specification documentation: https://spec.openapis.org/oas/v3.0.3
openapi: 3.0.3

definitions:
  Tutu:
    type: object
    properties:
      insee:
        type: string
      attribute:
        type: string

  Tata:
    type: object
    properties:
      id:
        type: integer
        format: int64
      pacage:
        type: string
      attribute:
        type: string
      statut:
        type: string
      tutu:
        $ref: '#/definitions/Tutu'
      dateHistorisation: 
        type: string
        format: date-time

  Toto:
    type: object
    properties:
      id:
        type: integer
        format: int64
      pacage:
        type: string
      attribute:
        type: string
      statut:
        type: string
      tutu:
        $ref: '#/definitions/Tutu'
      tataList:
        type: array
        items:  
          $ref: '#/definitions/Tata'

Generation Details

I am using the following maven configuration:

<plugin>
	<groupId>org.openapitools</groupId>
	<artifactId>openapi-generator-maven-plugin</artifactId>
        <version>5.1.0</version>
	<executions>
		<execution>
			<goals>
				<goal>generate</goal>
			</goals>
			<!-- openapi-generator-maven-plugin configuration documentation: https://github.com/OpenAPITools/openapi-generator/tree/master/modules/openapi-generator-maven-plugin -->
			<configuration>
				<inputSpec>openapi.yaml</inputSpec>
				<!-- https://openapi-generator.tech/docs/generators/#server-generators -->
				<generatorName>jaxrs-spec</generatorName>
				<modelNameSuffix>TO</modelNameSuffix>
				<!-- configOptions documentation for jaxrs-spec generator: https://openapi-generator.tech/docs/generators/jaxrs-spec/ -->
				<configOptions>
					<sourceFolder>src/main/java</sourceFolder>
					<interfaceOnly>true</interfaceOnly>
					<returnResponse>true</returnResponse>
					<serializableModel>true</serializableModel>
					<generatePom>false</generatePom>
				</configOptions>
			</configuration>
		</execution>
	</executions>
</plugin>

Steps to reproduce

1. run mvn clean install
2. look generated classes inside target/src/main/java/.../TotoApi.java to see @ApiOperation(value = "some badly encoded characters", notes = "", tags={ })
3. look generated doc inside target/src/main/openapi/openapi.yaml to see summary and description tags with badly encoded characters

Related issues/PRs

Suggest a fix

Start by running the Maven configuration against openapi.yaml and compare the French text in the generated target/src/main/java/.../TotoApi.java and target/src/main/openapi/openapi.yaml with the source. Check how the jaxrs-spec generator handles the encoding of summary and description values. Done means generated annotations and OpenAPI output preserve characters such as é correctly.