feat: implement MCP HTTP server endpoint with authentication (#18670)

# Add MCP HTTP server with streamable transport support

- Add MCP HTTP server with streamable transport support
- Integrate with existing toolsdk for Coder workspace operations
- Add comprehensive E2E tests with OAuth2 bearer token support
- Register MCP endpoint at /api/experimental/mcp/http with authentication
- Support RFC 6750 Bearer token authentication for MCP clients

Change-Id: Ib9024569ae452729908797c42155006aa04330af
Signed-off-by: Thomas Kosiewski <tk@coder.com>

coderd/mcp/mcp_test.go

@@ -0,0 +1,133 @@
+package mcp_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/mark3labs/mcp-go/mcp"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	mcpserver "github.com/coder/coder/v2/coderd/mcp"
+	"github.com/coder/coder/v2/codersdk"
+	"github.com/coder/coder/v2/codersdk/toolsdk"
+	"github.com/coder/coder/v2/testutil"
+)
+
+func TestMCPServer_Creation(t *testing.T) {
+	t.Parallel()
+
+	logger := testutil.Logger(t)
+
+	server, err := mcpserver.NewServer(logger)
+	require.NoError(t, err)
+	require.NotNil(t, server)
+}
+
+func TestMCPServer_Handler(t *testing.T) {
+	t.Parallel()
+
+	logger := testutil.Logger(t)
+
+	server, err := mcpserver.NewServer(logger)
+	require.NoError(t, err)
+
+	// Test that server implements http.Handler interface
+	var handler http.Handler = server
+	require.NotNil(t, handler)
+}
+
+func TestMCPHTTP_InitializeRequest(t *testing.T) {
+	t.Parallel()
+
+	logger := testutil.Logger(t)
+
+	server, err := mcpserver.NewServer(logger)
+	require.NoError(t, err)
+
+	// Use server directly as http.Handler
+	handler := server
+
+	// Create initialize request
+	initRequest := map[string]any{
+		"jsonrpc": "2.0",
+		"id":      1,
+		"method":  "initialize",
+		"params": map[string]any{
+			"protocolVersion": mcp.LATEST_PROTOCOL_VERSION,
+			"capabilities":    map[string]any{},
+			"clientInfo": map[string]any{
+				"name":    "test-client",
+				"version": "1.0.0",
+			},
+		},
+	}
+
+	body, err := json.Marshal(initRequest)
+	require.NoError(t, err)
+
+	req := httptest.NewRequest(http.MethodPost, "/", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Accept", "application/json,text/event-stream")
+
+	recorder := httptest.NewRecorder()
+	handler.ServeHTTP(recorder, req)
+
+	if recorder.Code != http.StatusOK {
+		t.Logf("Response body: %s", recorder.Body.String())
+	}
+	assert.Equal(t, http.StatusOK, recorder.Code)
+
+	// Check that a session ID was returned
+	sessionID := recorder.Header().Get("Mcp-Session-Id")
+	assert.NotEmpty(t, sessionID)
+
+	// Parse response
+	var response map[string]any
+	err = json.Unmarshal(recorder.Body.Bytes(), &response)
+	require.NoError(t, err)
+
+	assert.Equal(t, "2.0", response["jsonrpc"])
+	assert.Equal(t, float64(1), response["id"])
+
+	result, ok := response["result"].(map[string]any)
+	require.True(t, ok)
+
+	assert.Equal(t, mcp.LATEST_PROTOCOL_VERSION, result["protocolVersion"])
+	assert.Contains(t, result, "capabilities")
+	assert.Contains(t, result, "serverInfo")
+}
+
+func TestMCPHTTP_ToolRegistration(t *testing.T) {
+	t.Parallel()
+
+	logger := testutil.Logger(t)
+
+	server, err := mcpserver.NewServer(logger)
+	require.NoError(t, err)
+
+	// Test registering tools with nil client should return error
+	err = server.RegisterTools(nil)
+	require.Error(t, err)
+	require.Contains(t, err.Error(), "client cannot be nil", "Should reject nil client with appropriate error message")
+
+	// Test registering tools with valid client should succeed
+	client := &codersdk.Client{}
+	err = server.RegisterTools(client)
+	require.NoError(t, err)
+
+	// Verify that all expected tools are available in the toolsdk
+	expectedToolCount := len(toolsdk.All)
+	require.Greater(t, expectedToolCount, 0, "Should have some tools available")
+
+	// Verify specific tools are present by checking tool names
+	toolNames := make([]string, len(toolsdk.All))
+	for i, tool := range toolsdk.All {
+		toolNames[i] = tool.Name
+	}
+	require.Contains(t, toolNames, toolsdk.ToolNameReportTask, "Should include ReportTask (UserClientOptional)")
+	require.Contains(t, toolNames, toolsdk.ToolNameGetAuthenticatedUser, "Should include GetAuthenticatedUser (requires auth)")
+}