rename hasDarkBackground helper function and add docstring

Author: cemms1

dotcom-rendering/src/lib/cardHelpers.test.ts

@@ -1,7 +1,7 @@
 import type { DCRContainerPalette } from '../types/front';
-import { containerPaletteHasDarkBackground } from './cardHelpers';
+import { hasDarkBackground } from './cardHelpers';
 
-describe('cardHasDarkBackground', () => {
+describe('hasDarkBackground', () => {
 	const testCases = [
 		{
 			containerPalette: undefined,
@@ -35,9 +35,7 @@ describe('cardHasDarkBackground', () => {
 	it.each(testCases)(
 		'returns $expectedResult for $format format, $containerPalette containerPalette',
 		({ containerPalette, expectedResult }) => {
-			expect(containerPaletteHasDarkBackground(containerPalette)).toBe(
-				expectedResult,
-			);
+			expect(hasDarkBackground(containerPalette)).toBe(expectedResult);
 		},
 	);
 });

dotcom-rendering/src/lib/cardHelpers.ts

@@ -14,7 +14,14 @@ export const isMediaCard = (format: ArticleFormat): boolean => {
 	}
 };
 
-export const containerPaletteHasDarkBackground = (
+/**
+ * Determines whether the application of a container palette override
+ * results in a dark background for the container and cards inside it
+ *
+ * This is primarily used to decide whether to force usage of the logo
+ * for dark mode when it would otherwise be configured as light mode
+ */
+export const hasDarkBackground = (
 	containerPalette?: DCRContainerPalette,
 ): boolean => {
 	switch (containerPalette) {

dotcom-rendering/src/lib/decideLogo.ts

@@ -1,13 +1,12 @@
 import type { Branding } from '../types/branding';
 import type { DCRContainerPalette } from '../types/front';
-import { containerPaletteHasDarkBackground } from './cardHelpers';
+import { hasDarkBackground } from './cardHelpers';
 
 export const decideBrandingLogo = (
 	branding: Branding,
 	containerPalette?: DCRContainerPalette,
 ): Branding['logo'] => {
-	return containerPaletteHasDarkBackground(containerPalette) &&
-		branding.logoForDarkBackground
+	return hasDarkBackground(containerPalette) && branding.logoForDarkBackground
 		? branding.logoForDarkBackground
 		: branding.logo;
 };