feat: add mTLS client certificate support #424

Job	Run time
Cloud tests (Python 3.12)	33s
Test pip install (Python 3.11)	15s
Test coverage (Python 3.12)	35s
Test coverage (Python 3.14)	39s
Test coverage (Python 3.13)	34s
Test pip install (Python 3.13)	20s
Test pip install (Python 3.14)	22s
Test coverage (Python 3.11)	32s
Test pip install (Python 3.12)	17s
Unit tests on ubuntu-latest (Python 3.13)	31s
Unit tests on macos-latest (Python 3.11)	30s
Unit tests on ubuntu-latest (Python 3.11)	35s
Unit tests on macos-latest (Python 3.12)	22s
Unit tests on ubuntu-latest (Python 3.14)	35s
Unit tests on ubuntu-latest (Python 3.12)	28s
Unit tests on macos-latest (Python 3.13)	26s
Unit tests on macos-latest (Python 3.14)	24s
Unit tests on windows-latest (Python 3.12)	1m 23s
Unit tests on windows-latest (Python 3.13)	1m 9s
Unit tests on windows-latest (Python 3.14)	1m 30s
Unit tests on windows-latest (Python 3.11)	1m 13s
Integration tests on macos-latest (Python 3.14)	2m 21s
Integration tests on windows-latest (Python 3.13)	3m 19s
Integration tests on windows-latest (Python 3.12)	3m 30s
Integration tests on macos-latest (Python 3.12)	1m 49s
Integration tests on windows-latest (Python 3.14)	3m 23s
Integration tests on macos-latest (Python 3.13)	2m 8s
Integration tests on windows-latest (Python 3.11)	2m 53s
Integration tests on ubuntu-latest (Python 3.13)	1m 5s
Integration tests on ubuntu-latest (Python 3.12)	1m 8s
Integration tests on ubuntu-latest (Python 3.14)	1m 15s
Integration tests on ubuntu-latest (Python 3.11)	1m 4s
Integration tests on macos-latest (Python 3.11)	1m 53s
	39m 1s

Provide feedback