Implement CSRF token verification for OAuth example #5030

Job	Run time
check-docs	14s
cargo-hack	2m 42s
cargo-public-api-crates (axum)	31s
check	40s
cargo-public-api-crates (axum-core)	17s
cargo-deny check (advisories)	25s
dependencies-are-sorted	15s
cargo-deny check (bans licenses sources)	27s
Spell Check with Typos	5s
cargo-public-api-crates (axum-extra)	27s
cargo-public-api-crates (axum-macros)	16s
test-nightly	1m 26s
test-msrv	1m 53s
armv5te-unknown-linux-musleabi	38s
test-docs	1m 29s
test-versions (stable)	3m 1s
wasm32-unknown-unknown	16s
test-versions (beta)	2m 32s
	17m 34s

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