Add REST API

[sveetch]

This should be optional, enabled only when DRF is available. Add an extra requirement "api" to install DRF.

We aim for a read only API first. The write capacity may come in a future another issue.

This will need:

• Article Serializers;
• Category Serializers;
• Author Serializers;
• Article Viewsets;
• Category Viewsets;
• Author Viewsets
• Pagination enabled;
• Queryset have to respect the publication criterias and language;
• API URLs have to live in their own map apart so it can be mounted outside Lotus views path;
• API must be optional depending drf is installed or not (a new extra dependancies);
• Tests depending drf is installed or not, so we can check with/without it through a Tox environment;
• Look for possible resumed object payload in list and a more complete one from detail;

[sveetch]

At least to start a read only API although i can be a little risky to structure API code around read only, since write operations may sometime requires some changes.

[sveetch]

Also there is https://github.com/tfranzel/drf-spectacular which bring OpenAPI schema in more modern way that Swagger

[sveetch]

Detail payload may at least include related object listing like the views.

[sveetch]

It has been started in branch https://github.com/emencia/django-blog-lotus/tree/try_drf_addition, it's pretty basic, properly working and without test yet

[sveetch]

Finally after review for django-filter, currently i don't see any worth value to implement it for now. We will wait for a real use case in future after the first API release but removing it from todo list for now.

[sveetch]

Temporary branch for API beta is finished and delivered into v0.7.0 branch https://github.com/emencia/django-blog-lotus/tree/v0.7.0 to continue