[BUG][Java][RestTemplate] No OAuth Authentication in ApiClient#authentications Map

Description

ApiClient.java is missing the "OAuth2" Authentication which results in RestClientException because when invoking the generated endpoint-method it tries to find the "OAuth2" Authentication in its map but there is none:

    protected void init() {
        // Use RFC3339 format for date and datetime.
        // See http://xml2rfc.ietf.org/public/rfc/html/rfc3339.html#anchor14
        this.dateFormat = new RFC3339DateFormat();

        // Use UTC as the default time zone.
        this.dateFormat.setTimeZone(TimeZone.getTimeZone("UTC"));

        // Set default User-Agent.
        setUserAgent("Java-SDK");

        // Setup authentications (key: authentication name, value: authentication).
        authentications = new HashMap<String, Authentication>();
        authentications.put("XToken", new HttpBearerAuth("bearer"));
        // Prevent the authentications from being modified.
        authentications = Collections.unmodifiableMap(authentications);
    }

openapi-generator version

7.11.0
7.2.0

OpenAPI declaration file content or url

security:
  - XToken: [ ]
  - OAuth2: [ ]
paths:
  /v1/management/logs:
    get:
      description: 'Get all Logs'
      operationId: 'get-all-logs'
      tags:
        - 'management'
      security:
        - OAuth2: [ ]
      responses:
        200:
          description: 'OK'
          content:
            application/text:
              schema:
                type: string
schemas:
  securitySchemes:
    XToken:
      description: 'Must contain an encrypted X-Token.'
      type: http
      scheme: bearer
    OAuth2:
      description: 'Must contain a signed Access Token.'
      type: oauth2
      flows:
        implicit:
          authorizationUrl: 'http://localhost:9090'
          scopes:
            openid: 'default'

Fix I had to implement:

    private static final String OPENAPI_SECURITY_OAUTH2_NAME = "OAuth2";

    @SuppressWarnings("unchecked")
    protected void addOAuth2AccessToken(final ApiClient apiClient, final String accessToken) {
        try {
            final Field authenticationsField = apiClient.getClass().getDeclaredField("authentications");
            authenticationsField.setAccessible(true);

            final Map<String, Authentication> originalAuthentications = (Map<String, Authentication>) authenticationsField.get(apiClient);
            if (!originalAuthentications.containsKey(OPENAPI_SECURITY_OAUTH2_NAME)) {
                final Map<String, Authentication> fixedAuthentications = new HashMap<>(originalAuthentications);
                final OAuth oAuth = new OAuth();
                oAuth.setAccessToken(accessToken);
                fixedAuthentications.put(OPENAPI_SECURITY_OAUTH2_NAME, oAuth);
                authenticationsField.set(apiClient, Collections.unmodifiableMap(fixedAuthentications));
            }

            authenticationsField.setAccessible(false);
        } catch (final Exception e) {
            throw new RuntimeException(e);
        }
    }

Start with the generated Java RestTemplate ApiClient.java init() method and the supplied OpenAPI security declaration, comparing the OAuth2 and XToken schemes. Trace how generated endpoint methods look up authentications; done means an OAuth2-secured endpoint finds its authentication without RestClientException while existing XToken behavior remains intact.