MSC3861: allow overriding the introspection endpoint #2101

Job	Run time
lint-crlf	4s
lint-newsfile	33s
changes	2s
check-lockfile	6s
lint	55s
check-sampleconfig	44s
lint-pydantic	49s
check-schema-delta	38s
Typechecking	1m 37s
lint-clippy	0s
lint-clippy-nightly	0s
lint-readme	0s
lint-rustfmt	0s
linting-done	4s
calculate-test-jobs	7s
portdb (3.8, 11)	3m 6s
trial-olddeps	7m 23s
trial-pypy	0s
portdb (3.11, 15)	2m 53s
complement (monolith, SQLite)	12m 1s
complement (monolith, Postgres)	13m 57s
cargo-bench	0s
cargo-test	0s
complement (workers, Postgres)	20m 8s
sytest (focal)	8m 24s
trial (3.8, sqlite, all)	4m 59s
sytest (focal, postgres)	10m 23s
trial (3.8, postgres, 11, all)	11m 28s
sytest (focal, multi-postgres, workers)	13m 34s
trial (3.8, sqlite)	4m 33s
sytest (focal, multi-postgres, workers, asyncio)	19m 9s
export-data	2m 9s
tests-done	2s
	2h 19m 48s

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