feat: add oauth2 authentication method

[marie-j]

No description provided.

[deathiop]

Suggested change

	return callback('[OVH] failed to retrieveOAuth2 Access Token');
	return callback('[OVH] failed to retrieve OAuth2 Access Token');

[deathiop]

Would it be possible to extract some useful data to output?
It seems to contain something like that:

  output: {
    statusCode: 401,
    payload: {
      statusCode: 401,
      error: 'Unauthorized',
      message: 'Response Error: 401 null'
    },
    headers: {}
  }

[deathiop]

I'm not sure of what this is testing, expired or not, a unique call will always fetch a token.
I would write something like that, in my own classy JS style OFC

'GET /me with expired token': function (done) {
  'use strict';

  this.timeout(5000);

  // First call, expires soon
  nock('https://www.ovh.com/auth')
    .post('/oauth2/token')
    .reply(200, {
      'access_token': 'TOKEN1',
      'token_type': 'Bearer',
      'expires_in': 10,
      'scope': 'all'
    });

  // Refresh call
  nock('https://www.ovh.com/auth')
    .post('/oauth2/token')
    .reply(200, {
      'access_token': 'TOKEN2',
      'token_type': 'Bearer',
      'expires_in': 3599,
      'scope': 'all'
    });

  // Called once with TOKEN1
  nock('https://eu.api.ovh.com', {
    reqheaders: {
      authorization: 'Bearer TOKEN1',
    },
  })
    .get("/1.0/me")
    .reply(200, {"status": "ok1"});

  // Called again with TOKEN2, after the refresh
  nock('https://eu.api.ovh.com', {
    reqheaders: {
      authorization: 'Bearer TOKEN2',
    },
  })
    .get("/1.0/me")
    .reply(200, {"status": "ok2"});

  var rest = ovh(oauthConfig);

  rest.request('GET', '/me', function (err, msg) {
    assert.ok(!err);
    assert.equal(msg.status, 'ok1');

    const sleep = ms => new Promise(r => setTimeout(r, ms));
    sleep(2000);

    rest.request('GET', '/me', function (err, msg) {
      assert.ok(!err);
      assert.equal(msg.status, 'ok2');

      done();
    });
  });
},

[deathiop]

Should test for reqheaders: {authorization: 'Bearer ok'}

[deathiop]

Suggested change

	if (this.oauthConfig && (!this.accessToken || this.accessToken.expired())) {
	if (this.oauthConfig && (!this.accessToken || this.accessToken.expired(10))) {

Since the lib allows it, adding a time buffer might prevents some race condition with expired tokens.
go-ovh has a 10 seconds one, suggesting the same.