Improve header parsing and add tests #767

Job	Run time
Tests (ubuntu-latest, 7.2, lowest)	39s
Tests (ubuntu-latest, 7.2, highest)	32s
Tests (ubuntu-latest, 7.3, lowest)	25s
Tests (ubuntu-latest, 7.3, highest)	1m 7s
Tests (ubuntu-latest, 7.4, lowest)	32s
Tests (ubuntu-latest, 7.4, highest)	55s
Tests (ubuntu-latest, 8.0, lowest)	24s
Tests (ubuntu-latest, 8.0, highest)	1m 17s
Tests (ubuntu-latest, 8.1, lowest)	20s
Tests (ubuntu-latest, 8.1, highest)	1m 3s
Tests (ubuntu-latest, 8.2, lowest)	20s
Tests (ubuntu-latest, 8.2, highest)	1m 13s
Tests (ubuntu-latest, 8.3, lowest)	55s
Tests (ubuntu-latest, 8.3, highest)	1m 47s
Tests (windows-latest, 7.2, lowest)	1m 16s
Tests (windows-latest, 7.2, highest)	1m 27s
Tests (windows-latest, 7.3, lowest)	1m 24s
Tests (windows-latest, 7.3, highest)	2m 21s
Tests (windows-latest, 7.4, lowest)	1m 23s
Tests (windows-latest, 7.4, highest)	1m 45s
Tests (windows-latest, 8.0, lowest)	1m 15s
Tests (windows-latest, 8.0, highest)	2m 9s
Tests (windows-latest, 8.1, lowest)	1m 27s
Tests (windows-latest, 8.1, highest)	2m 49s
Tests (windows-latest, 8.2, lowest)	1m 2s
Tests (windows-latest, 8.2, highest)	2m 10s
Tests (windows-latest, 8.3, lowest)	1m 19s
Tests (windows-latest, 8.3, highest)	1m 37s
	34m 53s

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