POST /accounts/custom-field
Creates a new custom field for accounts. The field key is auto-generated from the label and cannot be set manually.
Key generation rule: Spaces are replaced with underscores, the result is uppercased, and _C is appended. Only spaces are transformed — all other characters pass through as-is.
Response
data
If a field with the same generated key already exists and is active, the request returns
409 Conflict.