The `eq()` function refines a `ItemsQueryBuilder` to match only items where the value of the specified `propertyName` equals the specified `value`.
`eq()` matches only values of the same type. For example, `0` stored as a number doesn't match `'0'` stored as a string.
Matching strings with `eq()` is case-sensitive, so `'text'` isn't equal to `'Text'`.