Improve /api/jobs handling of models with many to many relationships

[ojongerius]

Current implementation was a bit of a cop out: listing jobs will return the id instead of values for objects with many to many relationships. For example, look at the values for sites and labels:

HTTP 200 OK
Allow: GET, POST, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "count": 4,
    "next": null,
    "previous": null,
    "results": [
        {
            "id": 1,
            "title": "Reading Support Person",
            "text": "Volunteer will work either one-on-one or in a small group - no more than 4 - to help students increase reading mileage an d comprehension. Students often need help in developing vocabulary and reading strategies for unknown words. We have a hig h number of English language learners (ELL) and they benefit from having support in this area",
            "labels": [
                5
            ],
            "organisation": {
                "id": 1,
                "name": "Volunteer Wellington",
                "region": "wellington",
                "city": "wellington",
                "url": "https://www.volunteerwellington.org.nz/",
                "created_at": "2017-10-08T22:36:24.078728Z",
                "updated_at": "2017-10-08T22:36:24.103673Z"
            },
            "sites": [
                1
            ],
            "country": "new zealand",
            "region": "wellington",
            "created_at": "2017-10-08T22:36:23.965767Z",
            "updated_at": "2017-10-08T22:36:24.030438Z",
            "url": "https://seekvolunteer.co.nz/volunteering/49932/reading-support-person",
            "seen": 0
        },
        {
            "id": 2,
            "title": "Gardener",
            "text": "Basic gardening to ensure vegetable gardens remain weeded fertilised and watered in the spring and summer growing seasons . Every August we have a team of volunteers come in and prepare the gardens for spring but the gardens need ongoing mainte nance to ensure they are as productive as possible. Ideal role for a Karori local to come once or twice a week to maintain  and water garden and ensure planting happens at right times for Karori climate but anyone keen is welcome",
            "labels": [
                4
            ],
            "organisation": {
                "id": 1,
                "name": "Volunteer Wellington",
                "region": "wellington",
                "city": "wellington",
                "url": "https://www.volunteerwellington.org.nz/",
                "created_at": "2017-10-08T22:36:24.078728Z",
                "updated_at": "2017-10-08T22:36:24.103673Z"
            },
            "sites": [
                1
            ],
            "country": "new zealand",
            "region": "wellington",
            "created_at": "2017-10-08T22:36:23.965767Z",
            "updated_at": "2017-10-08T22:36:24.030438Z",
            "url": "https://seekvolunteer.co.nz/volunteering/49914/gardener",
            "seen": 0
        },
        {
            "id": 3,
            "title": "Companion Volunteer",
            "text": "Provide safe companionship and support to the person with dementia for 1-2 hours weekly or fortnightly. This may include (but is not limited to) tasks such as visiting a cafe or library, going for a walk, making a cup of tea, reading the newsp aper together, watching sport etc. Police check required. TRAINING: Initial induction of two 2-hour sessions and ongoing o ptional training throughout the year. How to Apply",
            "labels": [
                5
            ],
            "organisation": {
                "id": 2,
                "name": "Dementia Canterbury",
                "region": "canterbury",
                "city": "christchurch",
                "url": "https://www.dementiacanterbury.org.nz/",
                "created_at": "2017-10-08T22:36:24.078728Z",
                "updated_at": "2017-10-08T22:36:24.103673Z"
            },
            "sites": [
                2
            ],
            "country": "new zealand",
            "region": "wellington",
            "created_at": "2017-10-08T22:36:23.965767Z",
            "updated_at": "2017-10-08T22:36:24.030438Z",
            "url": "https://dogoodjobs.co.nz/jobs/companion-volunteer",
            "seen": 0
        },
        {
            "id": 4,
            "title": "Nappy changer",
            "text": "This is a great opportunity for young and old",
            "labels": [
                5
            ],
            "organisation": {
                "id": 1,
                "name": "Volunteer Wellington",
                "region": "wellington",
                "city": "wellington",
                "url": "https://www.volunteerwellington.org.nz/",
                "created_at": "2017-10-08T22:36:24.078728Z",
                "updated_at": "2017-10-08T22:36:24.103673Z"
            },
            "sites": [
                2
            ],
            "country": "new zealand",
            "region": "otago",
            "created_at": "2017-10-08T22:36:23.965767Z",
            "updated_at": "2017-10-08T22:36:24.030438Z",
            "url": "https://dogoodjobs.co.nz/nappy-changer",
            "seen": 0
        }
    ]
}

This was an easy way of getting the API working with many2many relationships for both getting and creating nested structures like the Job model.

DoD:

• Getting items from the jobs endpoints will expend nested models Labels and Sites will expand them, when updating job.
• Creating or updating Jobs allows either passing in the id, or passing in the nested structure.

See:

• http://www.django-rest-framework.org/api-guide/relations/