CourseState - Add label field

[jbpenrath]

Sometimes, we do not want to concat the course state text with its datetime but we simply want to display a label which explicit the course state.

So we could assume to add a label property to the CourseState dict output.

STATE_LABELS = {
    ONGOING_OPEN: _("On going and still opened for enrollment"),
    FUTURE_OPEN: _("Opened for enrollment"),
    ARCHIVED_OPEN: _("Archived but opened for enrollment"),
    FUTURE_NOT_YET_OPEN: _("Not yet opened for enrollment"),
    FUTURE_CLOSED: _("Not yet started"),
    ONGOING_CLOSED: _("On-going"),
    ARCHIVED_CLOSED: _("Archived"),
    TO_BE_SCHEDULED: _("To be scheduled"),
}

[jbpenrath]

After some thoughts, I'm not quit sure this is relevant to add those kind of labels to backend. Indeed, the label to display really depend to the user context. As a learner, if I'm not yet enrolled to the course, I surely want to know if enrollment are still opened and when the course will begin. Then if the learner is enrolled, enrollment dates are no more relevant. Now, from a course leader point of view, maybe only course dates are relevant (when the course will start? It is ongoing ? When it will be ended ?)
Then from an content editor point of view, maybe it's relevant to display both information : what is the course state ? what is the enrollment state ?

Ping @PanchoutNathan