fix(Nextcloud Node): Throw an actual error if server responded with Fatal error (#8234)

## Summary
Nextcloud and Yourls receiving response with OK status as string
containing 'Fatal error', throw an actual error in such case

![image](https://github.com/n8n-io/n8n/assets/88898367/7cba4b8c-3b34-476f-8a35-e10738022427)

## Related tickets and issues

https://linear.app/n8n/issue/NODE-1035/nextcloud-and-yourls-throw-an-actual-error-if-server-responded-with

packages/nodes-base/nodes/NextCloud/GenericFunctions.ts

@@ -1,4 +1,4 @@
-import type { IExecuteFunctions, IHookFunctions } from 'n8n-workflow';
+import { NodeOperationError, type IExecuteFunctions, type IHookFunctions } from 'n8n-workflow';
 
 import type { OptionsWithUri } from 'request';
 
@@ -52,5 +52,18 @@ export async function nextCloudApiRequest(
 
 	const credentialType =
 		authenticationMethod === 'accessToken' ? 'nextCloudApi' : 'nextCloudOAuth2Api';
-	return this.helpers.requestWithAuthentication.call(this, credentialType, options);
+
+	const response = await this.helpers.requestWithAuthentication.call(this, credentialType, options);
+
+	if (typeof response === 'string' && response.includes('<b>Fatal error</b>')) {
+		throw new NodeOperationError(
+			this.getNode(),
+			"NextCloud responded with a 'Fatal error', check description for more details",
+			{
+				description: `Server response:\n${response}`,
+			},
+		);
+	}
+
+	return response;
 }

packages/nodes-base/nodes/Yourls/GenericFunctions.ts

@@ -37,6 +37,16 @@ export async function yourlsApiRequest(
 			);
 		}
 
+		if (typeof response === 'string' && response.includes('<b>Fatal error</b>')) {
+			throw new NodeOperationError(
+				this.getNode(),
+				"Yourls responded with a 'Fatal error', check description for more details",
+				{
+					description: `Server response:\n${response}`,
+				},
+			);
+		}
+
 		return response;
 	} catch (error) {
 		throw new NodeApiError(this.getNode(), error as JsonObject);