e2ee-api: Add documentation

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>
7 jobs for master in 2 minutes and 38 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #21073
allowed to fail
pylint-plugins

00:01:29

passed #21070
pytest-3.5

00:00:43

passed #21071
pytest-3.6

00:00:43

passed #21072
pytest-latest

00:00:42

passed #21069
security-check

00:00:30

 
  Build
passed #21074
www
build-doc

00:01:09

passed #21075
build-ubuntu

00:00:20