Adds how-to guide on adding authorities to access tokens

Closes gh-542

docs/src/main/java/sample/customClaims/CustomClaimsConfiguration.java

@@ -0,0 +1,22 @@
+package sample.customClaims;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.oauth2.server.authorization.OAuth2TokenType;
+import org.springframework.security.oauth2.server.authorization.token.JwtEncodingContext;
+import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenCustomizer;
+
+@Configuration
+public class CustomClaimsConfiguration {
+	@Bean
+	public OAuth2TokenCustomizer<JwtEncodingContext> jwtTokenCustomizer() {
+		return (context) -> {
+			if (OAuth2TokenType.ACCESS_TOKEN.equals(context.getTokenType())) {
+				context.getClaims().claims((claims) -> {
+					claims.put("claim-1", "value-1");
+					claims.put("claim-2", "value-2");
+				});
+			}
+		};
+	}
+}

docs/src/main/java/sample/customClaims/authorities/CustomClaimsWithAuthoritiesConfiguration.java

@@ -0,0 +1,44 @@
+package sample.customClaims.authorities;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.core.authority.AuthorityUtils;
+import org.springframework.security.core.userdetails.User;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.security.core.userdetails.UserDetailsService;
+import org.springframework.security.oauth2.server.authorization.OAuth2TokenType;
+import org.springframework.security.oauth2.server.authorization.token.JwtEncodingContext;
+import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenCustomizer;
+import org.springframework.security.provisioning.InMemoryUserDetailsManager;
+
+import java.util.Collections;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+@Configuration
+public class CustomClaimsWithAuthoritiesConfiguration {
+	@Bean
+	public UserDetailsService users() {
+		UserDetails user = User.withDefaultPasswordEncoder()
+				.username("user1") // <1>
+				.password("password")
+				.roles(new String[] { "user", "admin" }) // <2>
+				.build();
+		return new InMemoryUserDetailsManager(user);
+	}
+
+	@Bean
+	public OAuth2TokenCustomizer<JwtEncodingContext> jwtTokenCustomizer() { // <3>
+		return (context) -> {
+			if (OAuth2TokenType.ACCESS_TOKEN.equals(context.getTokenType())) { // <4>
+				context.getClaims().claims((claims) -> { // <5>
+					Set<String> roles = AuthorityUtils.authorityListToSet(context.getPrincipal().getAuthorities())
+							.stream()
+							.map(c -> c.replaceFirst("^ROLE_", ""))
+							.collect(Collectors.collectingAndThen(Collectors.toSet(), Collections::unmodifiableSet)); // <6>
+					claims.put("roles", roles); // <7>
+				});
+			}
+		};
+	}
+}