Add a field for custom headers

[nicosabena]

The underlying oauth2 strategy supports a customHeaders value for the options, where you can specify custom headers to be send in the OAuth HTTP interactions. customHeaders is a hash, with header names and values:

    "options": {
      "client_id": "xxxxx",
      "client_secret": "xxxxx",
      "authorizationURL": "xxxx",
      "tokenURL": "xxxx",
      "scope": "",
      "customHeaders": {
          "Header1": "Value2"
          "Header2": "Value2"
      },
      "scripts": {
        "fetchUserProfile": "xxxx"
      }

It would be nice if the extension allowed for providing this custom headers.
Being able to set customHeaders in a custom connection enables special use cases such as OAuth identity providers that require credentials as HTTP Basic authentication (in a Authorization header).

[jcenturion]

@nicosabena: I've already added support for customHeaders. Closing this bug :).

[nicosabena]

Thanks!