This is the first step for #1847596: Deprecate Taxonomy term reference field in favor of Entity-reference
Started code in branch er-autocreate-1847924 chez yched.
First working patch. Added "auto-create" settings.
Patch is against #1801304: Add Entity reference field
Working on tests...
Closing in favor of the main issue
...then lets make it a duplicate instead, because having an issue status say "fixed" might give the (wrong) impression that what it's title states has actually been implemented.
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