Template envelope for a single teaser field: which display modes the
author is allowed to choose right now, given the active billing plan,
the underlying property data, and the parent context (project /
property pre-market / room).
allowedDisplays
Type: enum
Display modes the author may choose for this field right now —
a subset of actual, hidden, span, custom_span.
Fields with no allowed mode (plan-locked, no underlying value, or
extra-confidential) are absent from the parent template object.