Add OAuth 2.1 + PKCE + DCR authentication for MCP server

bazel/java.MODULE.bazel

@@ -20,7 +20,10 @@ maven.install(
         "com.fasterxml.jackson.datatype:jackson-datatype-jsr310",
         "com.fasterxml.jackson.module:jackson-module-scala_2.13",
         "com.google.guava:guava:33.5.0-jre",
+        "com.nimbusds:nimbus-jose-jwt:9.47",
+        "com.nimbusds:oauth2-oidc-sdk:11.21",
         "io.micronaut:micronaut-inject",
+        "io.modelcontextprotocol.sdk:mcp:0.12.1",
         "io.micronaut:micronaut-inject-java",
         "io.micronaut.validation:micronaut-validation",
         "io.micronaut.validation:micronaut-validation-processor",
@@ -34,10 +37,11 @@ maven.install(
         "io.netty:netty-codec",
         "io.netty:netty-handler",
         "io.netty:netty-transport",
-        "io.sentry:sentry-logback:8.26.0",
+        "io.sentry:sentry-logback:8.30.0",
         "jakarta.annotation:jakarta.annotation-api:3.0.0",
         "junit:junit:4.13.2",
         "org.assertj:assertj-core:3.27.6",
+        "org.bouncycastle:bcprov-jdk18on:1.83",
         "org.eclipse.jetty:jetty-server:%s" % JETTY_VERSION,
         "org.eclipse.jetty.websocket:websocket-jetty-server:%s" % JETTY_VERSION,
         "org.jspecify:jspecify:1.0.0",

jvm/src/main/java/com/muchq/mcpclient/BUILD.bazel

@@ -0,0 +1,22 @@
+load("@rules_java//java:java_library.bzl", "java_library")
+
+java_library(
+    name = "config",
+    srcs = ["McpClientConfig.java"],
+    visibility = [
+        "//jvm/src/main/java/com/muchq/mcpclient:__subpackages__",
+        "//jvm/src/test/java/com/muchq/mcpclient:__subpackages__",
+    ],
+)
+
+java_library(
+    name = "mcpclient",
+    srcs = ["McpClientWrapper.java"],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":config",
+        "//jvm/src/main/java/com/muchq/mcpclient/oauth",
+        "@maven//:io_modelcontextprotocol_sdk_mcp",
+        "@maven//:org_slf4j_slf4j_api",
+    ],
+)

jvm/src/main/java/com/muchq/mcpclient/McpClientConfig.java

@@ -0,0 +1,125 @@
+package com.muchq.mcpclient;
+
+/**
+ * Configuration for the MCP OAuth client.
+ *
+ * This configuration is used to:
+ * - Connect to the MCP server
+ * - Identify the client during OAuth registration
+ * - Configure the local OAuth callback server
+ * - Select transport type (HTTP or SSE)
+ */
+public class McpClientConfig {
+
+    /**
+     * Transport type for MCP communication.
+     */
+    public enum TransportType {
+        /** Streamable HTTP transport (request/response). */
+        HTTP,
+        /** Server-Sent Events transport (streaming). */
+        SSE
+    }
+
+    private final String serverUrl;
+    private final String clientName;
+    private final String clientVersion;
+    private final int callbackPort;
+    private final String clientId;
+    private final String clientSecret;
+    private final TransportType transportType;
+
+    private McpClientConfig(Builder builder) {
+        this.serverUrl = builder.serverUrl;
+        this.clientName = builder.clientName;
+        this.clientVersion = builder.clientVersion;
+        this.callbackPort = builder.callbackPort;
+        this.clientId = builder.clientId;
+        this.clientSecret = builder.clientSecret;
+        this.transportType = builder.transportType;
+    }
+
+    public String getServerUrl() {
+        return serverUrl;
+    }
+
+    public String getClientName() {
+        return clientName;
+    }
+
+    public String getClientVersion() {
+        return clientVersion;
+    }
+
+    public int getCallbackPort() {
+        return callbackPort;
+    }
+
+    public String getClientId() {
+        return clientId;
+    }
+
+    public String getClientSecret() {
+        return clientSecret;
+    }
+
+    public TransportType getTransportType() {
+        return transportType;
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static class Builder {
+        private String serverUrl;
+        private String clientName = "MCP Java Client";
+        private String clientVersion = "1.0.0";
+        private int callbackPort = 8888;
+        private String clientId;
+        private String clientSecret;
+        private TransportType transportType = TransportType.HTTP;
+
+        public Builder serverUrl(String serverUrl) {
+            this.serverUrl = serverUrl;
+            return this;
+        }
+
+        public Builder clientName(String clientName) {
+            this.clientName = clientName;
+            return this;
+        }
+
+        public Builder clientVersion(String clientVersion) {
+            this.clientVersion = clientVersion;
+            return this;
+        }
+
+        public Builder callbackPort(int callbackPort) {
+            this.callbackPort = callbackPort;
+            return this;
+        }
+
+        public Builder clientId(String clientId) {
+            this.clientId = clientId;
+            return this;
+        }
+
+        public Builder clientSecret(String clientSecret) {
+            this.clientSecret = clientSecret;
+            return this;
+        }
+
+        public Builder transportType(TransportType transportType) {
+            this.transportType = transportType;
+            return this;
+        }
+
+        public McpClientConfig build() {
+            if (serverUrl == null || serverUrl.isEmpty()) {
+                throw new IllegalArgumentException("serverUrl is required");
+            }
+            return new McpClientConfig(this);
+        }
+    }
+}