Add metatags for custom paths (not routes)

Roman Gudevrequested to merge
issue/metatag-3537900:3537900-add-metatags-for-custom-paths into 2.1.x

Issue #3356420 by DamienMcKenna, jwilson3, PapaGrande: Character count on fields via Maxlength integration.

Closes #3537900

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