Thread safety of client-v2 Client

Documentation for client-v2 never explicitly states that Client class is thread-safe or not. From code it appears to be thread-safe, but it would be very useful to have an official confirmation on whether the same Client object can be reused across threads or it should be created per thread.

Start by reviewing the client-v2 Client documentation and implementation to determine whether one Client object can be reused across threads. Document the official thread-safety guidance, including whether callers should share a Client or create one per thread; the issue does not identify a specific documentation file or test.

Written by the indexing model from the issue text.