design: Add design doc for managed configuration #8062

Job	Run time
build (no git)	1m 30s
test (linux-x86_64-gnu)	6m 25s
test (linux-aarch64-gnu)	6m 20s
check (rustfmt)	30s
check (clippy)	1m 23s
check (cargo-deny, advisories)	23s
test (macos-aarch64)	5m 54s
test (macos-x86_64)	17m 14s
check (doctests)	2m 56s
test (windows-x86_64)	15m 40s
check (cargo-deny, bans)	25s
check (cargo-deny, licenses)	24s
check (latest mkdocs, optional)	18s
check (zizmor)	15s
check (cargo-deny, sources)	23s
test (windows-aarch64)	16m 28s
check (mkdocs)	18s
check (codespell)	12s
check (Cargo.lock dependency count)	6s
check (protos)	39s
nix flake (ubuntu-24.04)	8m 13s
nix flake (ubuntu-24.04-arm)	7m 47s
nix flake (macos-14)	10m 33s
required checks (merge queue)	0s
	1h 44m 16s

Provide feedback