Ktor extensions for streamable http (#504)

## Motivation and Context
Adds Ktor extensions for streaming data over the server-side HTTP
transport

## How Has This Been Tested?
Integration test

## Breaking Changes
-

## Types of changes
- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [x] My code follows the repository's style guidelines
- [x] New and existing tests pass locally
- [x] I have added appropriate error handling
- [x] I have added or updated documentation as needed

integration-test/src/jvmTest/kotlin/io/modelcontextprotocol/kotlin/sdk/integration/streamablehttp/AbstractStreamableHttpIntegrationTest.kt

@@ -0,0 +1,82 @@
+package io.modelcontextprotocol.kotlin.sdk.integration.streamablehttp
+
+import io.ktor.serialization.kotlinx.json.json
+import io.ktor.server.application.install
+import io.ktor.server.cio.CIOApplicationEngine
+import io.ktor.server.engine.EmbeddedServer
+import io.ktor.server.engine.embeddedServer
+import io.ktor.server.plugins.contentnegotiation.ContentNegotiation
+import io.modelcontextprotocol.kotlin.sdk.server.Server
+import io.modelcontextprotocol.kotlin.sdk.server.ServerOptions
+import io.modelcontextprotocol.kotlin.sdk.server.mcpStreamableHttp
+import io.modelcontextprotocol.kotlin.sdk.types.GetPromptResult
+import io.modelcontextprotocol.kotlin.sdk.types.Implementation
+import io.modelcontextprotocol.kotlin.sdk.types.McpJson
+import io.modelcontextprotocol.kotlin.sdk.types.PromptArgument
+import io.modelcontextprotocol.kotlin.sdk.types.PromptMessage
+import io.modelcontextprotocol.kotlin.sdk.types.Role
+import io.modelcontextprotocol.kotlin.sdk.types.ServerCapabilities
+import io.modelcontextprotocol.kotlin.sdk.types.TextContent
+import io.ktor.server.cio.CIO as ServerCIO
+
+open class AbstractStreamableHttpIntegrationTest {
+
+    suspend fun initTestServer(name: String? = null): StreamableHttpTestServer {
+        val mcpServer = Server(
+            Implementation(name = name ?: DEFAULT_SERVER_NAME, version = VERSION),
+            ServerOptions(
+                capabilities = ServerCapabilities(prompts = ServerCapabilities.Prompts(listChanged = true)),
+            ),
+        ) {
+            addPrompt(
+                name = "prompt",
+                description = "Prompt description",
+                arguments = listOf(
+                    PromptArgument(
+                        name = "client",
+                        description = "Client name who requested a prompt",
+                        required = true,
+                    ),
+                ),
+            ) { request ->
+                GetPromptResult(
+                    messages = listOf(
+                        PromptMessage(
+                            role = Role.User,
+                            content = TextContent("Prompt for client ${request.params.arguments?.get("client")}"),
+                        ),
+                    ),
+                    description = "Prompt for ${request.params.name}",
+                )
+            }
+        }
+
+        val ktorServer = embeddedServer(
+            ServerCIO,
+            host = URL,
+            port = PORT,
+        ) {
+            install(ContentNegotiation) {
+                json(McpJson)
+            }
+            mcpStreamableHttp { mcpServer }
+        }
+
+        return StreamableHttpTestServer(
+            mcpServer = mcpServer,
+            ktorServer = ktorServer.startSuspend(wait = false),
+        )
+    }
+
+    data class StreamableHttpTestServer(
+        val mcpServer: Server,
+        val ktorServer: EmbeddedServer<CIOApplicationEngine, CIOApplicationEngine.Configuration>,
+    )
+
+    companion object {
+        internal const val DEFAULT_SERVER_NAME = "streamable-http-test-server"
+        internal const val VERSION = "1.0.0"
+        internal const val URL = "127.0.0.1"
+        internal const val PORT = 0
+    }
+}

integration-test/src/jvmTest/kotlin/io/modelcontextprotocol/kotlin/sdk/integration/streamablehttp/StreamableHttpIntegrationTest.kt

@@ -0,0 +1,65 @@
+package io.modelcontextprotocol.kotlin.sdk.integration.streamablehttp
+
+import io.ktor.client.HttpClient
+import io.ktor.client.plugins.sse.SSE
+import io.modelcontextprotocol.kotlin.sdk.client.Client
+import io.modelcontextprotocol.kotlin.sdk.client.StreamableHttpClientTransport
+import io.modelcontextprotocol.kotlin.sdk.types.GetPromptRequest
+import io.modelcontextprotocol.kotlin.sdk.types.GetPromptRequestParams
+import io.modelcontextprotocol.kotlin.sdk.types.Implementation
+import io.modelcontextprotocol.kotlin.sdk.types.LATEST_PROTOCOL_VERSION
+import io.modelcontextprotocol.kotlin.sdk.types.TextContent
+import io.modelcontextprotocol.kotlin.test.utils.actualPort
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.runBlocking
+import kotlin.test.Test
+import kotlin.test.assertTrue
+import io.ktor.client.engine.cio.CIO as ClientCIO
+
+class StreamableHttpIntegrationTest : AbstractStreamableHttpIntegrationTest() {
+
+    @Test
+    fun `client should receive responses via POST json and server notifications via GET sse`() =
+        runBlocking(Dispatchers.IO) {
+            var server: StreamableHttpTestServer? = null
+            var client: Client? = null
+            var httpClient: HttpClient? = null
+
+            try {
+                server = initTestServer()
+                val port = server.ktorServer.actualPort()
+
+                httpClient = HttpClient(ClientCIO) { install(SSE) }
+                val transport = StreamableHttpClientTransport(
+                    client = httpClient,
+                    url = "http://$URL:$port/mcp",
+                ).apply {
+                    protocolVersion = LATEST_PROTOCOL_VERSION
+                }
+
+                client = Client(Implementation("streamable-http-client", VERSION))
+                client.connect(transport)
+
+                val prompt = getPrompt(client, "Client A")
+                assertTrue { "Client A" in prompt }
+            } finally {
+                client?.close()
+                httpClient?.close()
+                server?.ktorServer?.stopSuspend(1000, 2000)
+            }
+        }
+
+    private suspend fun getPrompt(client: Client, clientName: String): String {
+        val response = client.getPrompt(
+            GetPromptRequest(
+                GetPromptRequestParams(
+                    name = "prompt",
+                    arguments = mapOf("client" to clientName),
+                ),
+            ),
+        )
+
+        return (response.messages.first().content as? TextContent)?.text
+            ?: error("Failed to receive prompt for Client $clientName")
+    }
+}