Project Dataset Details API

[jachro]

As a renku-graph API user, I'd like to be able to fetch details of a Dataset with the given identifier that belongs to a project with the given slug.

Acceptance criteria:

• KG service to expose a new GET /knowledge-graph/projects/:namespace/:name/datasets/:id
• the API to respond 404 NOT_FOUND when
  • no project with the given slug is found
  • no dataset with the given identifier if found
  • user has no access to the project
• for successfully found dataset, an 200 OK response is returned with the following JSON payload:

  {
    "_links": [
      {
        "rel":  "self",
        "href": "https://zemdgsw:9540/datasets/22222222222222222222222222222222"
      },
      {
        "rel":  "initial-version",
        "href": "https://zemdgsw:9540/datasets/11111111111111111111111111111111"
      },
      {
        "rel":  "tags",
        "href": "https://zemdgsw:9540/knowledge-graph/projects/namespace1/project1-name/datasets/dataset-name/tags"
      }
    ],
    "identifier": "22222222222222222222222222222222",
    "versions": {
      "initial": "11111111111111111111111111111111"
    },
    "name":        "dataset-name",
    "slug":        "dataset-name",
    "url":         "http://host/url1",             // optional property
    "sameAs":      "http://host/url2",             // optional property when no "derivedFrom" exists
    "derivedFrom": "http://host/url1",             // optional property when no "sameAs" exists
    "description": "vbnqyyjmbiBQpubavGpxlconuqj",  // optional property
    "published": {
      "datePublished": "2012-10-14",               // optional property
      "creator": [
        {
          "name":        "e wmtnxmcguz",
          "affiliation": "SDSC"                    // optional property
        },
        {
          "name":  "iilmadw vcxabmh",
          "email": "ticUnrW@cBmrdomoa"             // optional property
        }
      ]
    },
    "created":      "2012-10-15T03:02:25.639Z",    // optional property
    "dateModified": "2012-11-15T03:02:25.639Z",    // optional property,
    "hasPart": [
      {
        "atLocation": "data/dataset-name/file1"
      },
      {
        "atLocation": "data/dataset-name/file2"
      }
    ],
    "project":  {
      "_links": [
        {
          "rel":  "project-details",
          "href": "https://zemdgsw:9540/projects/namespace1/project1-name"
        }
      ],
      "dataset": {
        "identifier": "22222222-2222-2222-2222-222222222222"
      },
      "path":       "namespace1/project1-name",
      "slug":       "namespace1/project1-name",
      "name":       "project1 name",
      "visibility": "public"
    },
    "keywords": [ "rldzpwo", "gfioui" ],
    "images": [
      {
        "location": "image.png",
        "_links":[
          {
            "rel":  "view",
            "href": "https://renkulab.io/gitlab/project_path/raw/master/data/mniouUnmal/image.png"
          }
        ]
      },
      {
        "location": "http://host/external-image.png",
        "_links":[
          {
            "rel":  "view",
            "href": "http://host/external-image.png"
          }
        ]
      }
    ]
  }