simple namespace implementation added

[tompesman]

Only thing i've added is the options parameter to find_serializer_class_name method so that it can use the options[:namespace] parameter to prefix the class lookup: "#{options[:namespace]}::#{object.class.name}Serializer". The sub serializers are namespaced as well.

Usage:
JSONAPI::Serializer.serialize(object, namespace: ::MyApi)
or
JSONAPI::Serializer.serialize(object, namespace: '::MyApi')

No test or documentation at the moment, but if this PR is acceptable I can make them.

[fotinakis]

Nice! Quick questions:
Does the explicit serializer discovery not do what you want? https://github.com/fotinakis/jsonapi-serializers#explicit-serializer-discovery -- Perhaps you are trying to fix the API::V1/API::V2 problem? If so, then you'll need to make sure the tests cover the recursive include case, but this looks like a simple direction to me.

[tompesman]

Explicit discovery only maps a model to a single serializer. My use case is an application with multiple API backends. So, yes, I'm solving a similar problem: API::A/API::B. I saw another PR which was a bit too complicated. I think this is less intrusive. 😃

Can you explain the recursive include case to me?

[fotinakis]

Sounds right! For the recursive case just make sure that included relationships also handle this correctly (it looks like you're passing it down the find_recursive_relationships correctly, but the test should make sure) — something like https://github.com/fotinakis/jsonapi-serializers/blob/v0.13.0/spec/serializer_spec.rb#L695

[tompesman]

In which order should the serializer lookup work, we have:

• jsonapi_serializer_class_name
• namespace option
• default

I think jsonapi_serializer_class_name and the namespace should be switched. Because jsonapi_serializer_class_name is fixed to a class and the namespace is an option. So a developer could for example use the option for a single API request and the jsonapi_serializer_class_name for the other calls.

[tompesman]

Specs, Readme and 'lookup preference' updated.

[tompesman]

Added fix to pass the namespace to the include serialization. Not sure how to test this correctly.

[fotinakis]

Drop these meta attributes, they're not doing anything as far as I can tell.

[fotinakis]

Slowly getting back to this, this looks good to me! One comment above about some cleanup and then good to go.

[tompesman]

Updated the PR according to your feedback.

[fotinakis]

Released in gem v0.14.0, thanks for your contribution!

[tompesman]

Awesome! Thank you for merging and releasing! 👍