Detect use of UI5 release that is out of maintenance or scheduled for CDN removal

[boghyon]

In addition to my previous requests:

• Detect UI5 "Default Version" Bootstrap #789
• Promote "Renovate" docs#108

Even if a project specifies a UI5 version somewhere in an attempt to avoid the "Default Version", at some point, the UI5 release of the specified version will be outdated and, in case of CDN, eventually removed from the cloud entirely.

If a project uses an outdated UI5 version either via CDN, UI5 Tooling or SAP Fiori tools, UI5 linter detecting it would improve the chance to alert the owner of the project early in this regard.

In the report:

• Error if CDN is detected, as the outdated version will be removed soon. Warning otherwise.
• Possible solutions: similar to those from #789.

[flovogt]

JIRA: CPOUI5FOUNDATION-1050

[boghyon]

Out of UI5 linter scope but while we're at it:

@margopolo @KlattG @flovogt @jdichev
I'd even vote for displaying a message strip in the UI at runtime; in Demo Kit as well as all apps if affected.
And in case of CDN: a fat warning dialog

[codeworrior]

I'd even vote for displaying a message strip in the UI at runtime; in Demo Kit as well as all apps if affected.
And in case of CDN: a fat warning dialog

This was discussed when "end-of-cloud-provisioning" and Evergreen were introduced. At least in UI5 1.x there was no fully compatible way to inject this into an otherwise unknown HTML page (app). We can discuss this for 2.x again, constraints there are a bit different as bootstrap will always be async.

The other counter argument at that time was that the message reaches end users but should better reach admins / developers. We have no mean to distinguish those scenarios, however.

Adding @petermuessig as he was the driver of the discussion at that time.