Write documentation for authorization API

[th1agoalmeida]

controllers/kicking_concern.rb implements all of our authorization logic in the following methods

kick dont_kick dont_kick_people

they should fall under Goal Authentication.
Please implement documentation anywhere on README.MD explaining how they work.

Do not care so much about where to place the content as it can be moved in the future.

all controllers inside app/controllers implement at least one of the three methods mentioned above.

they do a "pre-authorization" step based on the user model which can be easily...

1. extended by altering user.rb (view issue Extract code from UserModelRoles #12 )
2. extended or replaced by other authorization gems such as cancan, pundit etc...
3. or both 😄

Also note they work at both instance and class level, wrapping a before_action call

Please also open any issues regarding the implementation of KickingConcern if you think it is suitable.