feat: add geo filter envelope support

src/protocol/search/filters/geo.ts

@@ -13,7 +13,7 @@
  * this program. If not, see <https://www.gnu.org/licenses/>.
  */
 // tslint:disable-next-line:no-implicit-dependencies
-import {Polygon} from 'geojson';
+import {Polygon, Position} from 'geojson';
 import {SCThingsField} from '../../../meta';
 import {SCSearchAbstractFilter, SCSearchAbstractFilterArguments} from '../filter';
 
@@ -29,6 +29,24 @@ export interface SCGeoFilter extends SCSearchAbstractFilter<SCGeoFilterArguments
   type: 'geo';
 }
 
+/**
+ * A rectangular geo shape, representing the top-left and bottom-right corners
+ *
+ * This is an extension of the Geojson type
+ * http://geojson.org/geojson-spec.html
+ */
+export interface Envelope {
+  /**
+   * The top-left and bottom-right corners of the bounding box
+   */
+  coordinates: [Position, Position];
+
+  /**
+   * The type of the geometry
+   */
+  type: 'envelope';
+}
+
 /**
  * Arguments for filter instruction by geo data
  */
@@ -41,7 +59,7 @@ export interface SCGeoFilterArguments extends SCSearchAbstractFilterArguments {
   /**
    * Geo data to check up on
    */
-  shape: Polygon;
+  shape: Polygon | Envelope;
 
   /**
    * Spatial relation between the provided shape and the shape of the field.