Default $http params serializer that converts objects to strings according to the following rules:

• {'foo': 'bar'} results in foo=bar
• {'foo': Date.now()} results in foo=2015-04-01T09%3A50%3A49.262Z (toISOString() and encoded representation of a Date object)
• {'foo': ['bar', 'baz']} results in foo=bar&foo=baz (repeated key for each array element)
• {'foo': {'bar':'baz'}} results in foo=%7B%22bar%22%3A%22baz%22%7D" (stringified and encoded representation of an object)

Note that serializer will sort the request parameters alphabetically.