Add mit-alert-banner component for NDE banner display

[adamshire123]

Why these changes are being introduced:

We wanted to add a customizeable alert banner to NDE.

How this addresses that need:

Created a new standalone Angular component (mit-alert-banner) that:

• Fetches translated banner text from the 'mit.alertBanner' label via TranslateService
• Displays HTML markup via [innerHTML] binding
• Conditionally renders above the Header using @if, hiding when label empty string (by setting mit.alertBanner to NOT_DEFINED)
• Reactively updates when language changes via onLangChange observable
• Includes comprehensive unit tests with detailed comments for maintainability

Side effects of this change:

• Requires 'mit.alertBanner' label to be configured in Alma's Custom Defined Labels table
• Component is hidden when label is set to NOT_DEFINED or returns empty string

Relevant ticket(s):

• https://mitlibraries.atlassian.net/browse/NDE-162

[Copilot]

Pull request overview

This PR introduces a new standalone Angular component (mit-alert-banner) intended to display a configurable/translatable alert banner above the NDE header via the existing custom-element mapping mechanism.

Changes:

• Added MitAlertBannerComponent that reads banner HTML from TranslateService and conditionally renders it via Angular control flow.
• Added unit tests covering creation, show/hide behavior, language-change updates, and @Input key override behavior.
• Wired the component into the custom-component selector mapping so it renders before the header.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/app/mit-alert-banner/mit-alert-banner.component.ts	Implements the banner’s translation lookup/reactivity and exposes an overridable label key.
src/app/mit-alert-banner/mit-alert-banner.component.html	Conditionally renders banner HTML when non-empty.
src/app/mit-alert-banner/mit-alert-banner.component.scss	Adds (currently empty) stylesheet entry for the banner component.
src/app/mit-alert-banner/mit-alert-banner.component.spec.ts	Adds unit tests for render/hide and language-change update behavior.
src/app/custom1-module/customComponentMappings.ts	Registers the banner to render before the header (nde-header-before).

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/app/mit-alert-banner/mit-alert-banner.component.ts:24

• bannerText only recomputes when onLangChange emits; changing the labelKey input at runtime won’t update the banner (even though the component API/comment says it can be overridden via binding). Include labelKey changes in the reactive pipeline so the banner updates when either the language or the key changes.

  bannerText = toSignal(
    this.translate.onLangChange.pipe(
      startWith(null),
      map(() => this.translate.instant(this.labelKey()).trim()),
    ),

[djanelle-mit]

@adamshire123 Styles and markup adjustments for the alert banner are committed! We can start reviewing whenever.