[confluence] documentation of token authentication

[kblase]

This is just a small contribution for the docs to help clarify the usage of Confluence Token in OnPrem Server and Data Center versions.

It should close this Issue and help clarify wrong informations:

911

It relates to these two tickets since there are also some informations about the login Process that are missguiding:

1070

332

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (1ccaa1b) 34.37% compared to head (714b1e0) 34.37%. Report is 1 commits behind head on master.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1288 +/- ## ======================================= Coverage 34.37% 34.37% ======================================= Files 45 45 Lines 8235 8235 Branches 1145 1145 ======================================= Hits 2831 2831 Misses 5290 5290 Partials 114 114 ```

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