Refines a query to match items whose specified property value starts with a specified string.
The startsWith() function refines a PublicPlansQueryBuilder to
only match items where the value of the specified property starts with the
defined string. Matching with startsWith() is case-sensitive, so "TEXT" does not start with "tex".
You can only use startsWith() with a property whose value is a String.
The property whose value will be compared with the string.
Supported property: slug
The string to look for at the beginning of the specified property value.