Implement GSSAPI authentication #526

Job	Run time
test-postgres (9.5)	5m 7s
test-platforms (3.8, ubuntu-latest, asyncio)	5m 19s
test-postgres (9.6)	3m 56s
test-platforms (3.8, ubuntu-latest, uvloop)	3m 29s
test-postgres (10)	4m 28s
test-platforms (3.8, macos-latest, asyncio)	2m 57s
test-postgres (11)	3m 57s
test-platforms (3.8, macos-latest, uvloop)	3m 51s
test-postgres (12)	4m 55s
test-platforms (3.8, windows-latest, asyncio)	5m 48s
test-postgres (13)	3m 51s
test-platforms (3.9, ubuntu-latest, asyncio)	4m 49s
test-postgres (14)	3m 59s
test-platforms (3.9, ubuntu-latest, uvloop)	5m 17s
test-postgres (15)	3m 57s
test-platforms (3.9, macos-latest, asyncio)	5m 12s
test-postgres (16)	4m 55s
test-platforms (3.9, macos-latest, uvloop)	2m 37s
test-platforms (3.9, windows-latest, asyncio)	5m 20s
test-platforms (3.10, ubuntu-latest, asyncio)	3m 20s
test-platforms (3.10, ubuntu-latest, uvloop)	4m 9s
test-platforms (3.10, macos-latest, asyncio)	3m 35s
test-platforms (3.10, macos-latest, uvloop)	3m 0s
test-platforms (3.10, windows-latest, asyncio)	6m 9s
test-platforms (3.11, ubuntu-latest, asyncio)	3m 39s
test-platforms (3.11, ubuntu-latest, uvloop)	3m 24s
test-platforms (3.11, macos-latest, asyncio)	3m 9s
test-platforms (3.11, macos-latest, uvloop)	3m 59s
test-platforms (3.11, windows-latest, asyncio)	5m 24s
test-platforms (3.12, ubuntu-latest, asyncio)	3m 28s
test-platforms (3.12, macos-latest, asyncio)	3m 41s
test-platforms (3.12, windows-latest, asyncio)	6m 22s
Regression Tests	1s
	2h 17m 4s

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