Update an existing custom field. You can update the label, description, required status, field type, and choices.

Important Notes:

• Field name cannot be changed after creation
• fieldType can be changed only when every non-empty stored value is already valid for the new type
  (values are never converted). Any type change is allowed on a field with no values. Otherwise the
  request fails with 422; typeChange reports how many values fail, out of how many, plus a
  sample of records and values to fix or clear first.
• When changing to dropdown or multi_select, send choices in the same request — stored values
  are checked against them
• currency exists only on contract-type fields
• When updating choices for dropdown or multi_select fields, provide the complete new array
• Changing appliesTo will affect which entities can use this field

Common Updates:

Update Label:

{
  "label": "Updated Label"
}

Update Dropdown Choices:

{
  "choices": ["New Option 1", "New Option 2", "New Option 3"]
}

Make Field Required:

{
  "required": true
}

Change a Text Field of Links to URL:

{
  "fieldType": "url"
}