Add mcp-secure module: OAuth2 resource server, per-tool scopes, and MDC audit logging for an MCP server

- JWT bearer authentication via spring-boot-starter-oauth2-resource-server, validated against
  an RSA keypair DemoJwtIssuer generates and signs with locally, so the whole module runs and
  tests deterministically with no external Authorization Server.
- @PreAuthorize on @McpTool methods maps SCOPE_orders:read / SCOPE_orders:write to lookup_order
  and refund_order -- confirmed empirically that method security actually applies to a bean the
  MCP server autoconfiguration invokes via reflection, since it invokes the Spring-proxied bean.
- SecurityFilterChain requires authentication on every request, so tool discovery (initialize/
  tools-list) is rejected before it ever reaches the MCP dispatcher -- no anonymous tool listing.
- ToolAuditAspect logs every tool call through MDC (subject, scopes, tool, outcome), pinned to
  @Order(150) -- between AuthorizationInterceptorsOrder.PRE_FILTER (100) and PRE_AUTHORIZE (200)
  -- so it wraps @PreAuthorize's interceptor and still logs denied calls, not only successful
  ones. Verified with a real Logback ListAppender reading back real MDC contents.

Two real findings worth a note: Spring Boot 4.0 renamed spring-boot-starter-aop to
spring-boot-starter-aspectj (the old artifact stops existing after 4.0.0-M2); and Spring AI's
AbstractSyncMcpToolMethodCallback.createSyncErrorResult concatenates an exception's message with
its root cause's message, which duplicates the text when they're the same exception -- visible
directly in the captured output when @PreAuthorize denies a call ("Access Denied\nAccess Denied").

5/5 tests pass against a real running server over real Streamable HTTP, with real signed JWTs.

Co-Authored-By: Claude Sonnet 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01FtpJvZfg4nvLvtzgJTDWpB

mcp-secure/pom.xml

@@ -0,0 +1,93 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>org.springframework.boot</groupId>
+    <artifactId>spring-boot-starter-parent</artifactId>
+    <version>4.1.1</version>
+    <relativePath/>
+  </parent>
+
+  <groupId>com.ankurm</groupId>
+  <artifactId>mcp-secure</artifactId>
+  <version>1.0.0</version>
+  <name>mcp-secure</name>
+  <description>The mcp-server module's order-lookup tools, behind an OAuth2 resource server: JWT validation, a scope per tool, unauthenticated discovery rejected, and every call audit-logged through MDC.</description>
+
+  <properties>
+    <java.version>25</java.version>
+    <!-- Spring AI is not managed by the Spring Boot BOM: this pair is yours to keep compatible. -->
+    <spring-ai.version>2.0.1</spring-ai.version>
+  </properties>
+
+  <dependencyManagement>
+    <dependencies>
+      <dependency>
+        <groupId>org.springframework.ai</groupId>
+        <artifactId>spring-ai-bom</artifactId>
+        <version>${spring-ai.version}</version>
+        <type>pom</type>
+        <scope>import</scope>
+      </dependency>
+    </dependencies>
+  </dependencyManagement>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework.ai</groupId>
+      <artifactId>spring-ai-starter-mcp-server-webmvc</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-security</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-oauth2-resource-server</artifactId>
+    </dependency>
+
+    <!-- @EnableMethodSecurity's @PreAuthorize enforcement, and the audit-log aspect, both need
+         AspectJ's pointcut expression parser on the classpath even under plain proxy-based AOP
+         (no weaving happens, but AnnotationAwareAspectJAutoProxyCreator still needs the parser
+         to read @Aspect/@Pointcut syntax). In Spring Boot 4.0 the starter that supplies this was
+         renamed: spring-boot-starter-aop no longer exists past 4.0.0-M2. It is
+         spring-boot-starter-aspectj now. See the article's "going deeper" note. -->
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-aspectj</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>org.springframework.security</groupId>
+      <artifactId>spring-security-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <configuration>
+          <argLine>-Duser.timezone=UTC -Dstdout.encoding=UTF-8 -Dfile.encoding=UTF-8</argLine>
+        </configuration>
+      </plugin>
+    </plugins>
+  </build>
+</project>