feat: add untrusted footer parsing for key rotation #300

Job	Run time
Default Features (batteries_included + v4)	1m 7s
Security Audit	2m 43s
Test Suite (v2_public)	1m 13s
Test Suite (v1_local)	1m 18s
Test Suite (v2_local)	56s
Test Suite (v1_public)	57s
Test Suite (v3_public)	59s
Clippy (v1_public)	1m 8s
Clippy (v1_local)	45s
Test Suite (v4_public)	1m 0s
Clippy (v2_local)	1m 1s
Clippy (v3_public)	28s
Test Suite (v4_local)	1m 1s
Clippy (v2_public)	20s
Test Suite (v3_local)	57s
Clippy (v4_public)	26s
Clippy (v4_local)	35s
Clippy (v3_local)	37s
	17m 31s

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