Doc: Clarify API OAuth doc

[PLhuillery]

Checking for existing issue

• I have checked for existing issues

Describe the content you'd like to see

Issue

To use the API, 4 values are required:

    OAUTH_CONSUMER_KEY
    OAUTH_CONSUMER_SECRET
    API_OAUTH_TOKEN
    API_OAUTH_TOKEN_SECRET

It's however not explicity stated where/how to get those values.

Where

Here
And the API doc overall (same page)

Proposed fix

State how to get those.
CONSUMER TOKEN = CONSUMER KEY
OAUTH TOKEN = OAuth dance to be done

• provide some example

[cnivolle]

The bearer token is about to be released.
@davlgd can you check this issue to prepare the future auth page ?