Add URL and payload validation to conversation client tests (#265)

Conversation client tests only verified non-null responses without
validating HTTP requests. Tests now capture and assert on request
methods, URLs, query parameters, and JSON payloads.

## Changes

**Added `request_capture` fixture**
- Captures HTTP requests during tests via mock transport
- Exposes `last_request` property for validation
- Returns standard `Client` instance compatible with existing APIs

**Enhanced test assertions**
- HTTP method validation (GET, POST, PUT, DELETE)
- Exact URL path validation including route parameters
- Query parameter validation (e.g., `continuationToken`)
- JSON payload validation for create/update operations (simplified to
check 1 key field per test)
- Authorization header validation for token-based authentication

**Added token authorization test**
- New `test_get_conversations_with_token` validates Bearer tokens are
properly sent in the Authorization header

## Example

Before:
```python
async def test_create_conversation(self, mock_http_client, mock_account):
    response = await client.create(params)
    assert response.id is not None
```

After:
```python
async def test_create_conversation(self, request_capture, mock_account):
    response = await client.create(params)
    
    # Validate request
    request = request_capture._capture.last_request
    assert request.method == "POST"
    assert str(request.url) == "https://test.service.url/v3/conversations"
    
    payload = json.loads(request.content)
    assert payload["isGroup"] is True
```

Covers 10 methods across ConversationClient, ActivityOperations, and
MemberOperations, plus token authorization.

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packages/api/tests/conftest.py

@@ -240,6 +240,128 @@ def mock_http_client(mock_transport):
     return client
 
 
+@pytest.fixture
+def request_capture():
+    """Fixture to capture HTTP request details for testing.
+
+    Returns:
+        A Client instance with an attached `_capture` attribute containing the RequestCapture helper.
+        Access captured requests via `client._capture.last_request` or `client._capture.requests`.
+    """
+
+    class RequestCapture:
+        """Helper class to capture request details."""
+
+        def __init__(self):
+            self.requests: list[httpx.Request] = []
+
+        def handler(self, request: httpx.Request) -> httpx.Response:
+            """Handler that captures requests and returns mock responses."""
+            self.requests.append(request)
+
+            # Default response
+            response_data: Any = {
+                "ok": True,
+                "url": str(request.url),
+                "method": request.method,
+            }
+
+            # Handle specific endpoints with realistic responses
+            if "GetAadTokens" in str(request.url):
+                response_data = {
+                    "https://graph.microsoft.com": {
+                        "connectionName": "test_connection",
+                        "token": "mock_graph_token_123",
+                        "expiration": "2024-12-01T12:00:00Z",
+                    },
+                }
+            elif "/conversations/" in str(request.url) and str(request.url).endswith("/members"):
+                response_data = [
+                    {
+                        "id": "mock_member_id",
+                        "name": "Mock Member",
+                        "aadObjectId": "mock_aad_object_id",
+                    }
+                ]
+            elif "/conversations/" in str(request.url) and "/members/" in str(request.url) and request.method == "GET":
+                response_data = {
+                    "id": "mock_member_id",
+                    "name": "Mock Member",
+                    "aadObjectId": "mock_aad_object_id",
+                }
+            elif "/conversations" in str(request.url) and request.method == "GET":
+                response_data = {
+                    "conversations": [
+                        {
+                            "id": "mock_conversation_id",
+                            "conversationType": "personal",
+                            "isGroup": True,
+                        }
+                    ],
+                    "continuationToken": "mock_continuation_token",
+                }
+            elif "/conversations" in str(request.url) and request.method == "POST":
+                # Parse request body to check if activity is included
+                try:
+                    import json
+
+                    request_body = json.loads(request.content.decode("utf-8")) if request.content else {}
+                    has_activity = "activity" in request_body and request_body["activity"] is not None
+                except Exception:
+                    has_activity = True  # Default to including activity_id if we can't parse
+
+                response_data = {
+                    "id": "mock_conversation_id",
+                    "type": "message",
+                    "serviceUrl": "https://mock.service.url",
+                }
+                if has_activity:
+                    response_data["activityId"] = "mock_activity_id"
+            elif "/activities" in str(request.url):
+                if request.method == "POST":
+                    response_data = {
+                        "id": "mock_activity_id",
+                        "type": "message",
+                        "text": "Mock activity response",
+                    }
+                elif request.method == "PUT":
+                    response_data = {
+                        "id": "mock_activity_id",
+                        "type": "message",
+                        "text": "Updated mock activity",
+                    }
+                elif request.method == "GET":
+                    response_data = [
+                        {
+                            "id": "mock_member_id",
+                            "name": "Mock Member",
+                            "aadObjectId": "mock_aad_object_id",
+                        }
+                    ]
+
+            return httpx.Response(
+                status_code=200,
+                json=response_data,
+                headers={"content-type": "application/json"},
+            )
+
+        @property
+        def last_request(self) -> httpx.Request | None:
+            """Get the last captured request."""
+            return self.requests[-1] if self.requests else None
+
+        def clear(self):
+            """Clear all captured requests."""
+            self.requests.clear()
+
+    capture = RequestCapture()
+    transport = httpx.MockTransport(capture.handler)
+    client = Client(ClientOptions(base_url="https://mock.api.com"))
+    client.http._transport = transport
+    client._capture = capture  # type: ignore[attr-defined]  # Attach for test access
+    return client
+
+
 @pytest.fixture
 def mock_client_credentials():
     """Create mock client credentials for testing."""