Fix: response name and API tests

[haotianzhu]

Check List

• [x] Fix #46 (write the relative issue number)

• [x] Branch is up to date with master

• [x] Now it's a good time for reviewing

• [x] Branch should have prefix either "feature/" or "fix/"

Comment

1. change response.name => response.index
2. response.index will be auto-generated by the order of response in the response list
3. back-end will send response.index to front-end

I test following URL

1. GET /api/questions
2. POST /api/questions
3. GET/DELETE/PATCH /api/questions/{id}

They are good now

There is a detailed document about Question's URLs in the wiki https://github.com/rw-moore/SciLO/wiki/Question-API

Put 'closes #.' in your comment to auto-close the issue that your PR fixes (if such).

[haotianzhu]

You can always update the whole question byPATCH. Since PATCH is a partially updating method, If you want to set some fields as null, you always need to provide null value. For example, you want to reset question.responses as [ ] you need to

{
...
"responses" : [ ]
...
}

NOTE: you can partially update question. For example, you can

{
"title": "Mock Question 2 new",
}

to change the title only.

BUT for the nested field like TAG, RESPONSE You can partially update the whole RESPONSE field but not a specific sub-field in RESPONSE For example, currently question.tags has two TAG, one is fun another is color. You can

  "tags": [
    {
      "name": "fun new"
    },
    {
      "name": "color"
    }
  ],

to partial update whole question.tags only. 👍

But you can't partially update the tag fun to fun new, even you give the id (id will be ignored)

  "tags": [
    {
     "id": 1,
      "name": "fun new"
    }
  ],

This will make question.tags only contains one tag 👎

@TianqiCS