Add HAProxy example for single port operation (#16768) #457

Job	Run time
changes	1s
check-lockfile	7s
lint-crlf	3s
lint-newsfile	0s
check-sampleconfig	38s
check-schema-delta	36s
lint-clippy	26s
lint	54s
lint-clippy-nightly	30s
Typechecking	1m 21s
lint-pydantic	1m 1s
lint-rustfmt	18s
linting-done	9s
calculate-test-jobs	5s
trial-olddeps	6m 46s
complement (monolith, SQLite)	12m 25s
portdb (3.8, 11)	2m 46s
trial-pypy	0s
complement (monolith, Postgres)	13m 28s
portdb (3.11, 15)	2m 52s
complement (workers, Postgres)	20m 14s
cargo-bench	0s
cargo-test	0s
sytest (focal)	8m 23s
trial (3.8, sqlite, all)	4m 24s
sytest (focal, postgres)	10m 1s
trial (3.9, sqlite, all)	3m 58s
sytest (focal, multi-postgres, workers)	13m 40s
trial (3.10, sqlite, all)	4m 7s
sytest (focal, multi-postgres, workers, asyncio)	29m 33s
sytest (focal, asyncio)	9m 52s
trial (3.11, sqlite, all)	3m 14s
trial (3.12, sqlite, all)	3m 40s
sytest (focal, postgres, asyncio)	11m 56s
trial (3.8, postgres, 11, all)	9m 36s
sytest (testing, postgres)	10m 32s
trial (3.12, postgres, 16, all)	9m 0s
trial (3.8, sqlite)	4m 16s
export-data	2m 1s
tests-done	2s
	3h 22m 55s

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