Change /share to create geoposition, /geo?id to update by id

bin/database/database_provider.dart

@@ -231,6 +231,7 @@ class DatabaseProvider {
   }
 
   Future<Geoposition> updatePosition(
+    int id,
     double x,
     double y,
   ) async {
@@ -238,11 +239,13 @@ class DatabaseProvider {
 
     final results = await _dbConnection.execute(
       Sql.named('''
-      INSERT INTO geopositions (x_value, y_value, last_update, expires_at)
-      VALUES (@xValue, @yValue, NOW(), @expiresAt)
+      UPDATE geopositions
+      SET x_value = @xValue, y_value = @yValue, last_update = NOW(), expires_at = @expiresAt
+      WHERE id = @id
       RETURNING id, x_value, y_value, last_update, expires_at
       '''),
       parameters: {
+        'id': id,
         'xValue': x,
         'yValue': y,
         'expiresAt': expiresAt.toIso8601String(),