Polish OAuth2IntrospectionAuthenticatedPrincipal

Removed some duplication by delegating to
DefaultOAuth2AuthenticatedPrincipal

Changed order of listed interfaces to satisfy compiler issue. When
listed with OAuth2AuthenticatedPrincipal first, then
OAuth2ResourceServerBeanDefinitionParserTests would fail to import
OpaqueTokenBeanDefinitionParser. Switching
OAuth2AuthenticatedPrincipal with OAuth2IntrospectionClaimAccessor
resolved the compilation issue.

Issue gh-6489

oauth2/oauth2-resource-server/src/main/java/org/springframework/security/oauth2/server/resource/introspection/OAuth2IntrospectionAuthenticatedPrincipal.java

@@ -16,16 +16,13 @@
 
 package org.springframework.security.oauth2.server.resource.introspection;
 
-import static org.springframework.security.core.authority.AuthorityUtils.NO_AUTHORITIES;
-
 import java.io.Serializable;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Map;
 
 import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.oauth2.core.DefaultOAuth2AuthenticatedPrincipal;
 import org.springframework.security.oauth2.core.OAuth2AuthenticatedPrincipal;
-import org.springframework.util.Assert;
 
 /**
  * A domain object that wraps the attributes of OAuth 2.0 Token Introspection.
@@ -34,11 +31,9 @@ import org.springframework.util.Assert;
  * @since 5.4
  * @see <a target="_blank" href="https://tools.ietf.org/html/rfc7662#section-2.2">Introspection Response</a>
  */
-public final class OAuth2IntrospectionAuthenticatedPrincipal implements OAuth2AuthenticatedPrincipal,
-		OAuth2IntrospectionClaimAccessor, Serializable {
-	private final Map<String, Object> attributes;
-	private final Collection<GrantedAuthority> authorities;
-	private final String name;
+public final class OAuth2IntrospectionAuthenticatedPrincipal implements OAuth2IntrospectionClaimAccessor,
+		OAuth2AuthenticatedPrincipal, Serializable {
+	private final OAuth2AuthenticatedPrincipal delegate;
 
 	/**
 	 * Constructs an {@code OAuth2IntrospectionAuthenticatedPrincipal} using the provided parameters.
@@ -49,7 +44,7 @@ public final class OAuth2IntrospectionAuthenticatedPrincipal implements OAuth2Au
 	public OAuth2IntrospectionAuthenticatedPrincipal(Map<String, Object> attributes,
 			Collection<GrantedAuthority> authorities) {
 
-		this(null, attributes, authorities);
+		this.delegate = new DefaultOAuth2AuthenticatedPrincipal(attributes, authorities);
 	}
 
 	/**
@@ -62,11 +57,7 @@ public final class OAuth2IntrospectionAuthenticatedPrincipal implements OAuth2Au
 	public OAuth2IntrospectionAuthenticatedPrincipal(String name, Map<String, Object> attributes,
 			Collection<GrantedAuthority> authorities) {
 
-		Assert.notEmpty(attributes, "attributes cannot be empty");
-		this.attributes = Collections.unmodifiableMap(attributes);
-		this.authorities = authorities == null ?
-				NO_AUTHORITIES : Collections.unmodifiableCollection(authorities);
-		this.name = name == null ? getSubject() : name;
+		this.delegate = new DefaultOAuth2AuthenticatedPrincipal(name, attributes, authorities);
 	}
 
 	/**
@@ -76,7 +67,7 @@ public final class OAuth2IntrospectionAuthenticatedPrincipal implements OAuth2Au
 	 */
 	@Override
 	public Map<String, Object> getAttributes() {
-		return this.attributes;
+		return this.delegate.getAttributes();
 	}
 
 	/**
@@ -87,7 +78,7 @@ public final class OAuth2IntrospectionAuthenticatedPrincipal implements OAuth2Au
 	 */
 	@Override
 	public Collection<? extends GrantedAuthority> getAuthorities() {
-		return this.authorities;
+		return this.delegate.getAuthorities();
 	}
 
 	/**
@@ -95,7 +86,7 @@ public final class OAuth2IntrospectionAuthenticatedPrincipal implements OAuth2Au
 	 */
 	@Override
 	public String getName() {
-		return this.name;
+		return this.delegate.getName();
 	}
 
 	/**