Support Angular 15

[jattasNI]

🧹 Tech Debt

nimble-angular currently supports Angular 14 but the latest version is 15. We need to support the latest.

This is currently blocked on #810.

Once that is fixed we have two options:

1. migrate Nimble to only support 15. This is what we have done historically.
2. claim support for both 14 and 15. This should be possible now that both versions are on Ivy and it would make it easier for our clients to upgrade on their own cadence. But there are open questions:

• would we compile using 14 and claim it's forwards compatible? or compile using 15 and claim it's backwards compatible? are both of these possible?
• what testing do we need to do with each version? Probably both due to the issue below
• will this be made more difficult because of us extending internal Angular APIs (Nimble Angular extends the Angular public API #732)

@TrevorKarjanis did some research on these options and believes that 2 is possible but he won't have bandwidth to drive progress for a while.

[m-akinc]

In Angular 15 they reimplemented RouterLink (including merging it with RouterLinkWithHref), which will be a problem for our Nimble versions of the router link directives (e.g. NimbleAnchorRouterLinkWithHrefDirective, NimbleAnchorButtonRouterLinkWithHrefDirective, NimbleAnchorLinkRouterLinkWithHrefDirective, and NimbleBreadcrumbItemRouterLinkWithHrefDirective). The new way it's implemented bakes in the notion of being for a and area elements only. Previously this assumption was just in the selector, which we were able to override by providing our own version that extended the original. Now there's not a clear way to reuse their implementation for our link-related elements.

[PetitCalgon]

Angular 14 is now in LTS mode till november 2023.
https://angular.io/guide/releases#actively-supported-versions
An upgrade to Angular 15 or better Angular 16 should be considered quickly 😊

Thanks

[jattasNI]

@PetitCalgon thanks for your interest! It's always a struggle for us to prioritize this sustaining work but we agree we should upgrade before 14 stops being supported. We'll find a way to get to it eventually but if you happen to have bandwidth on your team to help, we'd be happy to collaborate!