fix(NcModal): make dark header configurable

Required to fix regression with Text in Viewer in Nextcloud 30, where we
still want a white viewer header.

Signed-off-by: Jonas <[email protected]>

src/components/NcModal/NcModal.vue

@@ -200,7 +200,7 @@ export default {
 			tabindex="-1">
 			<!-- Header -->
 			<transition name="fade-visibility" appear>
-				<div class="modal-header" data-theme-dark>
+				<div class="modal-header" v-bind="dataThemeDarkAttr">
 					<h2 v-if="name.trim() !== ''"
 						:id="'modal-name-' + randId"
 						class="modal-header__name">
@@ -455,6 +455,14 @@ export default {
 			default: false,
 		},
 
+		/**
+		 * Make the modal header appear dark.
+		 */
+		darkHeader: {
+			type: Boolean,
+			default: true,
+		},
+
 		/**
 		 * Selector for the modal container, pass `null` to prevent automatic container mounting
 		 */
@@ -568,6 +576,11 @@ export default {
 		nextButtonAriaLabel() {
 			return t('Next')
 		},
+		dataThemeDarkAttr() {
+			return this.darkHeader
+				? { 'data-theme-dark': true }
+				: {}
+		},
 	},
 
 	watch: {