[later phase] [needs design] UX for associating mismatched cardinality field instance (too little or too much) with a higher cardinality SDC prop (e.g. `type: array, maxItems: 5`)

Overview

📌 [later phase] Support matching `{type: array, …}` prop shapes Postponed added support for type: array, including for DynamicPropSources (aka finding an existing field instance whose cardinality fulfills the requirements of the SDC prop's shape).

However, that means lower-cardinality (e.g. max 3 values) field instances cannot populate higher-cardinality SDC props (e.g. max 20 items), and vice versa: higher-cardinality (e.g. max 50 values) field instances cannot populate lower-cardinality SDC props (e.g. max 20 items).
Hence we have this in place right now:

      if ($cardinality_in_json_schema !== $field_cardinality) {
        // For finite cardinalities, we can still allow a lower cardinality (>1)
        // field instance to be matched with a higher cardinality JSON schema.
        // For example: a `maxItems: 20` SDC prop could be populated by a field
        // instance with cardinality 5. But a single-cardinality field would not
        // make sense, because it's no longer an array.
        // All other cases would result in problematic UX.
        // @todo consider allowing/supporting (but needs UX to be designed first to disambiguate the cardinality mismatch):
        // 1. JSON schema cardinality `unlimited`, field cardinality 1–N => would mean only partially populating an array
        // 2. JSON schema cardinality `1-N`, field cardinality `unlimited` => would mean some structured data values would not be visible; the content author would need to either be informed only the first N would be visible, or they'd need to be able to pick specific values
        if (!($field_cardinality > 1 && $cardinality_in_json_schema > $field_cardinality)) {
          continue;
        }
      }

This issue exists for that @todo.

Proposed resolution

TBD, needs design. Significant mental model mismatch risks here! ⚠️

User interface changes