/// A numeric value with an associated unit-of-measure.
///
/// Corresponds to `gml:MeasureType` in ISO 19136. The `uom` field is a
/// URI or UCUM expression identifying the unit (e.g. `"m"`, `"deg"`,
/// `"urn:ogc:def:uom:OGC:1.0:metre"`).
///
/// # Examples
///
/// ```rust
/// use egml_core::model::basic::Measure;
///
/// let height = Measure { uom: "m".to_string(), value: 12.5 };
/// assert_eq!(height.value, 12.5);
/// ```