feat: support oidc restriction management in the settings

app/routes/settings/dialogs/add-group.tsx

@@ -0,0 +1,51 @@
+import { useMemo, useState } from 'react';
+import Dialog from '~/components/Dialog';
+import Input from '~/components/Input';
+
+interface AddGroupProps {
+	groups: string[];
+	isDisabled?: boolean;
+}
+
+export default function AddGroup({ groups, isDisabled }: AddGroupProps) {
+	const [group, setGroup] = useState('');
+
+	const isInvalid = useMemo(() => {
+		if (!group || group.trim().length === 0) {
+			// Empty group is invalid, but no error shown
+			return false;
+		}
+
+		if (groups.includes(group.trim())) {
+			return true;
+		}
+	}, [group, groups]);
+
+	return (
+		<Dialog>
+			<Dialog.Button isDisabled={isDisabled}>Add group</Dialog.Button>
+			<Dialog.Panel>
+				<Dialog.Title>Add group</Dialog.Title>
+				<Dialog.Text className="mb-4">
+					Add this group to a list of allowed groups that can authenticate with
+					Headscale via OIDC.
+				</Dialog.Text>
+				<input type="hidden" name="action_id" value="add_group" />
+				<Input
+					isRequired
+					label="Group"
+					description="The group to allow for OIDC authentication."
+					placeholder="admin"
+					name="group"
+					onChange={setGroup}
+					isInvalid={group.trim().length === 0 || isInvalid}
+				/>
+				{isInvalid && (
+					<p className="text-red-500 text-sm mt-2">
+						The group you entered already exists in the list of allowed groups.
+					</p>
+				)}
+			</Dialog.Panel>
+		</Dialog>
+	);
+}