Proof of concept: obligation highlighting

[markverstege]

Description
Provide obligation date highlighting for the endpoint versioning schedule. This will allow users to select a target "obligation milestone date" to visually see what endpoint versions are applicable obligations at that point in time. This feature should support retired, deprecated, active and future obligations.

[markverstege]

This proof of concept has been included in the "poc/obligation-date-highlighting" branch.

New obligation date selector

Selecting a date using the date picker

Highlighting all obligations
Once a date is selected, all endpoints are highlighted in accordance with that target date. If they are active, they are shown as green. If they are retired and no longer applicable, they are greyed out. This highlighting also shows emerging endpoint versions (due in the next 3 month), future endpoint versions (due more than 3 months in the future), and deprecated endpoint versions (obligations being phased out).

Note: the date selector is a floating element that scrolls vertically with the user for convenience.

Collapsing obligations
For convenience any future, retired or inactive endpoint versions are hidden to focus on active, emerging and deprecated obligations.

Legend
A legend is provided that offers descriptive information regarding the highlighting colours and their meaning.

[nils-work]

This change was incorporated into v1.17.0 of the Standards.