refactor: separate map feature queries and source records

src/sources/featureSource.js

@@ -0,0 +1,20 @@
+/** Semantic candidate operations supplied to search and annotation selection. */
+export const FEATURE_SOURCE_METHODS = Object.freeze([
+  'getAdministrativeAreas',
+  'getAreaGeometry',
+  'getNeighborhoodAreas',
+  'getStreetAreas',
+  'getStreetLines',
+  'getFootprints',
+  'getEnclosingAreas',
+  'getMonuments',
+  'getFocusFootprints',
+]);
+
+export function requireFeatureSource(source) {
+  for (const method of FEATURE_SOURCE_METHODS) {
+    if (typeof source?.[method] !== 'function')
+      throw new TypeError('Missing feature operation: ' + method);
+  }
+  return source;
+}