Send multiple Dynamics 365 Web API operations in a single OData batch request

Steps

1. Construct a POST request to https://{org}.crm.dynamics.com/api/data/vX.X/$batch with Content-Type multipart/mixed; boundary={batchBoundary}
2. Each operation in the batch is separated by the boundary string and contains its own HTTP method, relative URL, headers, and optional body
3. Group mutually dependent operations (e.g., create then relate) inside a change set, which is a nested multipart block that enforces atomicity within that group
4. Parse the multipart response body — each part contains the HTTP status and response body for the corresponding request
5. Operations outside a change set execute independently and are not rolled back if others fail