Implement CSRF token verification for OAuth example #5031

Job	Run time
cargo-hack	2m 54s
check	49s
check-docs	43s
cargo-public-api-crates (axum)	32s
cargo-public-api-crates (axum-core)	19s
cargo-deny check (advisories)	27s
dependencies-are-sorted	19s
Spell Check with Typos	7s
cargo-public-api-crates (axum-extra)	34s
cargo-deny check (bans licenses sources)	24s
cargo-public-api-crates (axum-macros)	19s
test-msrv	1m 52s
test-nightly	1m 19s
test-docs	1m 24s
armv5te-unknown-linux-musleabi	32s
test-versions (stable)	2m 40s
test-versions (beta)	2m 38s
wasm32-unknown-unknown	13s
	18m 5s

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