Remove support for CMS 4 #417
Description
When CMS 4 goes EOL, some modules will no longer be commercially supported in any form.
Post-stable release steps for CMS 6 will clean a lot of stuff up for us, but there are some manual steps we need to take.
Notes
Should we update the way the supported badge works? It could ping an API and check "is this supported?" and only render the supported badge if the module is actually supported. Then we don't have to remember to do this step every 2 years.
Still to decide
Should we add this to CMS 5 modules that "folded in"?
> ![CAUTION]
> This module does not have a CMS 6 compatible version because it has been incorporated into {module name}
> This module will be archived when CMS 5 reaches EOL - see the [support timeline](https://silverstripe.org/software/roadmap)
Should we add this to subsite like module that has a single CMS 6 version released though lost support?
> ![CAUTION]
> This module is not commercially supported for CMS 6
> This module is only commercially supported for CMS 5
> This module will loose commercial support when CMS 5 reaches EOL - see the [support timeline](https://silverstripe.org/software/roadmap)
(and also link to https://docs.silverstripe.org/en/5/project_governance/supported_modules/)
Should we also provide instructions / a link to "Become a maintainer"?
There should also be a new card that's actioned when CMS 5 goes EOL to update this to say that it's simply not supported
Acceptance Criteria
- Remove "supported" badge from readme for modules that lost support
- Update module-standardiser to badge link to the explict CMS version of docs showing supported modules
- For modules that lost support, update the CMS 5.4 / 5 equivalent branches to link to CMS 5 version of docs
- Update major release process docs to include a step to run module stanardiser after incrementing the supported version of CMS so that the badge linking to the docs updates