feat: cleanup oidc logic and surface errors better

app/routes/auth/login/oidc-error.tsx

@@ -0,0 +1,63 @@
+import { AlertCircle } from 'lucide-react';
+import Card from '~/components/Card';
+import Code from '~/components/Code';
+
+export function OidcErrorNotice({ code }: { code: string }) {
+	return (
+		<Card className="max-w-md m-4 sm:m-0 mb-4 sm:mb-4 border border-red-500">
+			<div className="flex items-center justify-between gap-4">
+				<Card.Title className="text-red-500">Configuration Issue(s)</Card.Title>
+				<AlertCircle className="w-6 h-6 mb-2 text-red-500" />
+			</div>
+			{getErrorMessage(code)}
+		</Card>
+	);
+}
+
+function getErrorMessage(code: string) {
+	switch (code) {
+		case 'error_no_query':
+			return (
+				<Card.Text>
+					The SSO provider did not correctly redirect back to Headplane with the
+					required parameters. Please ensure your SSO provider is configured
+					correctly.
+				</Card.Text>
+			);
+
+		case 'error_no_session':
+		case 'error_invalid_session':
+			return (
+				<Card.Text>
+					Unable to complete SSO login due to missing or invalid session data.
+					Ensure that your Headplane cookie configuration is correct and that
+					your browser is accepting cookies.
+				</Card.Text>
+			);
+
+		case 'error_no_sub':
+			return (
+				<Card.Text>
+					The SSO provider did not return a valid user identifier. Please ensure
+					your SSO provider is correctly configured to provide the{' '}
+					<Code>sub</Code> claim.
+				</Card.Text>
+			);
+
+		case 'error_auth_failed':
+			return (
+				<Card.Text>
+					Authentication with the SSO provider failed. Please tray again later.
+					Headplane logs may provide more information.
+				</Card.Text>
+			);
+
+		default:
+			return (
+				<Card.Text>
+					An unknown error occurred during OIDC authentication. Please try again
+					later.
+				</Card.Text>
+			);
+	}
+}