[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 ✅

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

@@           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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