I honestly think all you need to do is add
<service id="travel_oauth_server_auth" class="%travel_oauth_server_auth.class%" scope="request">
...
</service>
To your XML and get rid of the service definition in your YAML file, also I see 2 types of namespace roots travel vs Travel. You might still have to tag the service, see http://symfony.com/doc/current/book/forms.html#defining-your-forms-as-services
parameters:
travel_oauth_server_auth.class: Travel\HomeBundle\Form\Type\AuthorizeFormType
services:
travel_oauth_server_auth:
class: %travel_oauth_server_auth%
Was not correct to begin with, as you'd want
parameters:
travel_oauth_server_auth.class: "Travel\HomeBundle\Form\Type\AuthorizeFormType"
services:
travel_oauth_server_auth:
class: %travel_oauth_server_auth.class%
The error you are receiving
ParameterNotFoundException: The service "travel_oauth_server.authorize.form" has a dependency on a non-existent parameter "travel_oauth_server_auth" :(
is because of
<service id="travel_oauth_server.authorize.form" factory-method="createNamed" factory-service="form.factory" class="Symfony\Component\Form\Form">
<argument type="service" id="travel_oauth_server.authorize.form_type" />
<argument>%travel_oauth_server_auth%</argument>
</service>
The second passed argument in here is not found, and it really tries hard to tell you so :-) ( compared to any other "framework").