MB-26396: Handling documents with geopoints in slice format

+ The issue lies with parsing documents containing a geopoint
  in slice format - which wasn't handled.
+ Unit test that verifies the fix.

mapping/document.go

@@ -504,7 +504,7 @@ func (dm *DocumentMapping) processProperty(property interface{}, path []string,
 			}
 			dm.walkDocument(property, path, indexes, context)
 		}
-	case reflect.Map:
+	case reflect.Map, reflect.Slice:
 		if subDocMapping != nil {
 			for _, fieldMapping := range subDocMapping.Fields {
 				if fieldMapping.Type == "geopoint" {

mapping/mapping_test.go

@@ -869,19 +869,46 @@ func TestMappingForGeo(t *testing.T) {
 	mapping := NewIndexMapping()
 	mapping.DefaultMapping = thingMapping
 
-	x := struct {
+	geopoints := []interface{}{}
+
+	// geopoint as a struct
+	geopoints = append(geopoints, struct {
 		Name     string    `json:"name"`
 		Location *Location `json:"location"`
 	}{
-		Name: "marty",
+		Name: "struct",
 		Location: &Location{
 			Lon: -180,
 			Lat: -90,
 		},
-	}
+	})
 
-	doc := document.NewDocument("1")
+	// geopoint as a map
-	err := mapping.MapDocument(doc, x)
+	geopoints = append(geopoints, struct {
+		Name     string                 `json:"name"`
+		Location map[string]interface{} `json:"location"`
+	}{
+		Name: "map",
+		Location: map[string]interface{}{
+			"lon": -180,
+			"lat": -90,
+		},
+	})
+
+	// geopoint as a slice
+	geopoints = append(geopoints, struct {
+		Name     string        `json:"name"`
+		Location []interface{} `json:"location"`
+	}{
+		Name: "slice",
+		Location: []interface{}{
+			-180, -90,
+		},
+	})
+
+	for i, geopoint := range geopoints {
+		doc := document.NewDocument(string(i))
+		err := mapping.MapDocument(doc, geopoint)
 		if err != nil {
 			t.Fatal(err)
 		}
@@ -901,6 +928,7 @@ func TestMappingForGeo(t *testing.T) {
 		if !foundGeo {
 			t.Errorf("expected to find geo point, did not")
 		}
+	}
 }
 
 type textMarshalable struct {