rename 'docker_name' as 'slug + let the user choose it
points to be considered
- allowed value should be very strict (eg:
\A[a-z][0-9a-z-]+\z
) because it is used in many critical places (especially in code run as root) - disallow reserved names: root sshd cli (and maybe others)
- user may choose the short name but only at creation time: currently the short_name is used as a key for docker images and containers. Updating it requires some cooperation with the controller to avoid inconsistencies between the db and the registry. ==> the job creation form should warn that this name is not modifiable after webapp creation.