add more custom oauth examples

spring-5-security-oauth/src/main/java/com/baeldung/oauth2/CustomAuthorizationRequestResolver.java

@@ -47,4 +47,11 @@ public class CustomAuthorizationRequestResolver implements OAuth2AuthorizationRe
     private OAuth2AuthorizationRequest customizeAuthorizationRequest1(OAuth2AuthorizationRequest req) {
         return OAuth2AuthorizationRequest.from(req).state("xyz").build();
     }
+    
+    private OAuth2AuthorizationRequest customizeOktaReq(OAuth2AuthorizationRequest req) {
+        Map<String,Object> extraParams = new HashMap<String,Object>();
+        extraParams.putAll(req.getAdditionalParameters()); 
+        extraParams.put("idp", "https://idprovider.com");
+        return OAuth2AuthorizationRequest.from(req).additionalParameters(extraParams).build();
+    }
 }

spring-5-security-oauth/src/main/java/com/baeldung/oauth2/LinkedinTokenResponseConverter.java

@@ -0,0 +1,24 @@
+package com.baeldung.oauth2;
+
+import java.util.Map;
+
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.security.oauth2.core.OAuth2AccessToken;
+import org.springframework.security.oauth2.core.endpoint.OAuth2AccessTokenResponse;
+import org.springframework.security.oauth2.core.endpoint.OAuth2ParameterNames;
+
+public class LinkedinTokenResponseConverter implements Converter<Map<String, String>, OAuth2AccessTokenResponse> {
+
+    @Override
+    public OAuth2AccessTokenResponse convert(Map<String, String> tokenResponseParameters) {
+        String accessToken = tokenResponseParameters.get(OAuth2ParameterNames.ACCESS_TOKEN);
+        long expiresIn = Long.valueOf(tokenResponseParameters.get(OAuth2ParameterNames.EXPIRES_IN));
+        
+        OAuth2AccessToken.TokenType accessTokenType = OAuth2AccessToken.TokenType.BEARER;
+
+        return OAuth2AccessTokenResponse.withToken(accessToken)
+            .tokenType(accessTokenType)
+            .expiresIn(expiresIn)
+            .build();
+    }
+}