Make `relatedTo*` reserved field handles #5033

Job	Run time
ci / Code Quality / ECS / ECS	1m 7s
ci / Code Quality / PHPStan / PHPStan	3m 27s
ci / Code Quality / Prettier / check	46s
ci / Tests / PHP 8.0 on mysql	10m 6s
ci / Tests / PHP 8.0 on pgsql	11m 56s
ci / Tests / PHP 8.1 on mysql	11m 32s
ci / Tests / PHP 8.1 on pgsql	11m 48s
ci / Notify Slack / on success	2s
ci / Notify Slack / on cancelled	0s
ci / Notify Slack / on failure	0s
	50m 44s

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