WIP: refactor auth mecanism ot rely on id

[inkhey]

• Refactor auth to rely on id.
• add automated for email change issue : Endpoint /users/:id/email break cookie validity tracim#953

[coveralls]

Pull Request Test Coverage Report for Build 685

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.008%) to 91.694%

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Files with Coverage Reduction	New Missed Lines	%
tracim_backend/lib/utils/authentification.py	5	93.75%
tracim_backend/init.py	6	92.24%

Totals
Change from base Build 683:	0.008%
Covered Lines:	13932
Relevant Lines:	15194

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💛 - Coveralls