Generate MCP classes with OpenAPI Generator (#294)

- Add OpenAPI Generator to build system to automatically generate MCP
protocol data classes from the official schema.
- Configure code quality tools to exclude generated files
- Add deserialization test

## Motivation and Context

Writing classes by hand is error-prone, when json schema exists. See
#185,
Also, autogenerating model classes ensures the SDK is in sync with the
protocol and can quickly catch up with its changes (see #218)

## How Has This Been Tested?
Regression tests

## Breaking Changes
No

## Types of changes
<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->
- [ ] 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
<!-- Go over all the following points, and put an `x` in all the boxes
that apply. -->
- [x] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
<!-- Add any other context, implementation notes, or design decisions
-->

kotlin-sdk-core/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/models/ProgressNotificationsTest.kt

@@ -0,0 +1,71 @@
+package io.modelcontextprotocol.kotlin.sdk.models
+
+import io.kotest.matchers.shouldBe
+import io.modelcontextprotocol.kotlin.sdk.ProgressNotification
+import io.modelcontextprotocol.kotlin.sdk.RequestId
+import io.modelcontextprotocol.kotlin.sdk.shared.McpJson
+import kotlin.test.Test
+
+class ProgressNotificationsTest {
+
+    /**
+     * https://modelcontextprotocol.io/specification/2025-06-18/basic/utilities/progress#progress-flow
+     */
+    @Test
+    fun `Read ProgressNotifications with string token`() {
+        //language=json
+        val json = """
+            {
+              "jsonrpc": "2.0",
+              "method": "notifications/progress",
+              "params": {
+                "progressToken": "abc123",
+                "progress": 50,
+                "total": 100,
+                "message": "Reticulating splines..."
+              }
+            }
+        """.trimIndent()
+
+        val result = McpJson.decodeFromString<ProgressNotification>(json)
+
+        result shouldBe ProgressNotification(
+            params = ProgressNotification.Params(
+                progressToken = RequestId.StringId("abc123"),
+                progress = 50.0,
+                message = "Reticulating splines...",
+                total = 100.0,
+            ),
+        )
+    }
+
+    /**
+     * https://modelcontextprotocol.io/specification/2025-06-18/basic/utilities/progress#progress-flow
+     */
+    @Test
+    fun `Read ProgressNotifications with integer token`() {
+        //language=json
+        val json = """
+            {
+              "jsonrpc": "2.0",
+              "method": "notifications/progress",
+              "params": {
+                "progressToken": 100500,
+                "progress": 50,
+                "total": 100,
+                "message": "Reticulating splines..."
+              }
+            }
+        """.trimIndent()
+
+        val result = McpJson.decodeFromString<ProgressNotification>(json)
+        result shouldBe ProgressNotification(
+            params = ProgressNotification.Params(
+                progressToken = RequestId.NumberId(100500),
+                progress = 50.0,
+                message = "Reticulating splines...",
+                total = 100.0,
+            ),
+        )
+    }
+}