Fix Enum not correctly serialized with \http_build_query in guzzle

[WoutervanderLoopNL]

Query parameters are not correctly encoded when parameter is a enum:

current result:
page=1&fulfilment-method%5Bname%5D=FBR&fulfilment-method%5Bvalue%5D=FBR&status%5Bname%5D=OPEN&status%5Bvalue%5D=OPEN&change-interval-minute=1

• parameter is encoded with the value and name property of the enum (which is PHP default) name=FBR&value=FBR . although I should expect a string enum is encoded to a string by default in PHP, but thats actually not the case.

expected result:
page=1&fulfilment-method=FBR&status=OPEN&change-interval-minute=1

[WoutervanderLoopNL]

@casperbakker